diff --git a/面向对象学生系统/bll/clear_all_students.py b/面向对象学生系统/bll/clear_all_students.py
new file mode 100644
index 0000000..5c17a05
--- /dev/null
+++ b/面向对象学生系统/bll/clear_all_students.py
@@ -0,0 +1,2 @@
+def clear_all_students(self) -> None:
+    self.dal.clear_all_students()
diff --git a/面向对象学生系统/bll/delete_student.py b/面向对象学生系统/bll/delete_student.py
new file mode 100644
index 0000000..e7ed349
--- /dev/null
+++ b/面向对象学生系统/bll/delete_student.py
@@ -0,0 +1,5 @@
+def delete_student(self,sid:str)-> bool:
+    if not self.dal.check_student_exists(sid):
+        raise ValueError(f"学生ID{sid}不存在。")
+    return self.dal.delete_student(sid)
+
diff --git a/面向对象学生系统/bll/export_students.py b/面向对象学生系统/bll/export_students.py
new file mode 100644
index 0000000..b1a5c46
--- /dev/null
+++ b/面向对象学生系统/bll/export_students.py
@@ -0,0 +1,9 @@
+def export_students(self,file_path:str)-> bool:
+    student =self.dal.get_all_students()
+    try:
+        with open(file_path,'w',encoding='utf-8')as f:
+            json.dump([student.to_dict() for student in students],f,ensure_ascii=False,indent=4)
+        return True
+    except Exception as e:
+        print(f"导出学生数据到JOSN 时出错：{e}")
+        return False
\ No newline at end of file
diff --git a/面向对象学生系统/bll/get_avg_height.py b/面向对象学生系统/bll/get_avg_height.py
new file mode 100644
index 0000000..ed587f0
--- /dev/null
+++ b/面向对象学生系统/bll/get_avg_height.py
@@ -0,0 +1,6 @@
+def get_avg_height(self)-> float:
+    students =self.dal.get_all_students()
+    if not students:
+        return 0.0
+    total_height = sum(student.height for student in students)
+    return total_height/len(students)
\ No newline at end of file
diff --git a/面向对象学生系统/bll/get_student_by_count.py b/面向对象学生系统/bll/get_student_by_count.py
new file mode 100644
index 0000000..ad35983
--- /dev/null
+++ b/面向对象学生系统/bll/get_student_by_count.py
@@ -0,0 +1,2 @@
+def get_student_by_count(self)-> int:
+    return self.dal.get_student_by_count()
diff --git a/面向对象学生系统/bll/get_student_by_height.py b/面向对象学生系统/bll/get_student_by_height.py
new file mode 100644
index 0000000..22d42e6
--- /dev/null
+++ b/面向对象学生系统/bll/get_student_by_height.py
@@ -0,0 +1,3 @@
+def get_student_by_height(self,min_height:int,max_height:int)-> List[Student]:
+    students=self.dal.get_all_students()
+    return [s for s in students if min_height <= s.height <= max_height]
\ No newline at end of file
diff --git a/面向对象学生系统/bll/get_student_by_id.py b/面向对象学生系统/bll/get_student_by_id.py
new file mode 100644
index 0000000..6108267
--- /dev/null
+++ b/面向对象学生系统/bll/get_student_by_id.py
@@ -0,0 +1,8 @@
+def get_student_by_id(self,sid:str)-> Optional[Student]:
+    return self.dal.find_student_by_sid(sid)
+def get_student_by_name(self,name:str)-> List[Student]:
+    return self.dal.find_student_by_name(name)
+def get_student_by_class(self,class_name:str)-> List[Student]:
+    return self.dal.find_student_by_class_name(name)
+def get_all_students(self)-> List[Student]:
+    return self.dal.get_all_students()
diff --git a/面向对象学生系统/bll/get_students_by_age.py b/面向对象学生系统/bll/get_students_by_age.py
new file mode 100644
index 0000000..da3bba1
--- /dev/null
+++ b/面向对象学生系统/bll/get_students_by_age.py
@@ -0,0 +1,9 @@
+def get_students_by_age(self,min_age:int,max_age:int)->List[Student]:
+    today =date.today()
+    students = self.dal.get_all_students()
+    age_filtered_students=[]
+    for student in students:
+        age =today.year-student.birth_date.year-((today.month,today,day)<(student.birth_date.month,student.birth_date.day))
+        if min_age <=age<=max_age:
+            age_filtered_students.append(student)
+    return age_filtered_students
\ No newline at end of file
diff --git a/面向对象学生系统/bll/get_students_by_enrollment_year.py b/面向对象学生系统/bll/get_students_by_enrollment_year.py
new file mode 100644
index 0000000..29cbe39
--- /dev/null
+++ b/面向对象学生系统/bll/get_students_by_enrollment_year.py
@@ -0,0 +1,3 @@
+def get_students_by_enrollment_year(self,year:int)-> List[Student]:
+    students =self.dal.get_all_students()
+    return [student for student in students if student.enrollment_date.year ==year]
\ No newline at end of file
diff --git a/面向对象学生系统/bll/studentBLL.py b/面向对象学生系统/bll/studentBLL.py
new file mode 100644
index 0000000..e76d178
--- /dev/null
+++ b/面向对象学生系统/bll/studentBLL.py
@@ -0,0 +1,7 @@
+class StudentBll:
+    def __init__(self,dal:StudentDal):
+        self.dal=dal
+def delete_student(self,sid:str)-> bool:
+    if not self.dal.check_student_exists(sid):
+        raise ValueError(f"学生 ID {sid}不存在。")
+    return self.dal.delete_students(sid)
diff --git a/面向对象学生系统/bll/student_serive.py b/面向对象学生系统/bll/student_serive.py
new file mode 100644
index 0000000..0961a82
--- /dev/null
+++ b/面向对象学生系统/bll/student_serive.py
@@ -0,0 +1,117 @@
+from typing import List, Optional
+from models.student import Student
+from dal.idal import IStudentDAL
+from utils.validator import validate_student_data
+from utils.id_utils import is_valid_id_card
+
+
+class StudentService:
+    """学生信息业务逻辑层"""
+
+    def __init__(self, dal: IStudentDAL):
+        self.dal = dal
+
+    def add_student(self, student: Student) -> tuple[bool, str]:
+        """添加学生"""
+        # 数据验证
+        is_valid, msg = validate_student_data(student)
+        if not is_valid:
+            return False, msg
+
+        # 检查学号是否已存在
+        if self.dal.get_by_stu_id(student.stu_id):
+            return False, "学号已存在"
+
+        # 检查身份证号是否已存在
+        if self.dal.get_by_id(student.id_card):
+            return False, "身份证号已存在"
+
+        # 添加学生
+        success = self.dal.add_student(student)
+        return success, "添加成功" if success else "添加失败"
+
+    def delete_student(self, id_card: str) -> tuple[bool, str]:
+        """删除学生"""
+        if not is_valid_id_card(id_card):
+            return False, "无效的身份证号"
+
+        success = self.dal.delete_student(id_card)
+        return success, "删除成功" if success else "删除失败"
+
+    def update_student(self, student: Student) -> tuple[bool, str]:
+        """更新学生信息"""
+        # 数据验证
+        is_valid, msg = validate_student_data(student)
+        if not is_valid:
+            return False, msg
+
+        # 检查学生是否存在
+        existing = self.dal.get_by_id(student.id_card)
+        if not existing:
+            return False, "学生不存在"
+
+        # 检查学号是否被其他学生使用
+        stu_with_same_id = self.dal.get_by_stu_id(student.stu_id)
+        if stu_with_same_id and stu_with_same_id.id_card != student.id_card:
+            return False, "学号已被其他学生使用"
+
+        success = self.dal.update_student(student)
+        return success, "更新成功" if success else "更新失败"
+
+    def get_student_by_id(self, id_card: str) -> Optional[Student]:
+        """根据身份证号获取学生"""
+        if not is_valid_id_card(id_card):
+            return None
+        return self.dal.get_by_id(id_card)
+
+    def get_student_by_stu_id(self, stu_id: str) -> Optional[Student]:
+        """根据学号获取学生"""
+        return self.dal.get_by_stu_id(stu_id)
+
+    def get_all_students(self) -> List[Student]:
+        """获取所有学生"""
+        return self.dal.get_all()
+
+    def search_by_name(self, name: str) -> List[Student]:
+        """按姓名查询(模糊)"""
+        return self.dal.get_by_name(name)
+
+    def search_by_class(self, class_name: str) -> List[Student]:
+        """按班级查询(模糊)"""
+        return self.dal.get_by_class(class_name)
+
+    def search_by_major(self, major: str) -> List[Student]:
+        """按专业查询(模糊)"""
+        return self.dal.get_by_major(major)
+
+    def count_total_students(self) -> int:
+        """统计学生总数"""
+        return self.dal.count_students()
+
+    def count_by_major(self) -> dict:
+        """按专业统计人数"""
+        return self.dal.count_by_major()
+
+    def calculate_avg_height(self, group_by: str = None) -> dict:
+        """计算平均身高"""
+        students = self.dal.get_all()
+        if not group_by:
+            heights = [s.height for s in students if s.height is not None]
+            return {'all': sum(heights) / len(heights)} if heights else {'all': 0}
+
+        groups = {}
+        for student in students:
+            if student.height is None:
+                continue
+
+            key = getattr(student, group_by)
+            if key not in groups:
+                groups[key] = []
+            groups[key].append(student.height)
+
+        return {k: sum(v) / len(v) for k, v in groups.items()}
+
+    def clear_all_data(self) -> tuple[bool, str]:
+        """清空所有学生数据"""
+        success = self.dal.clear_all()
+        return success, "数据已清空" if success else "清空失败"
\ No newline at end of file
diff --git a/面向对象学生系统/bll/update_student_partial.py b/面向对象学生系统/bll/update_student_partial.py
new file mode 100644
index 0000000..9d9752f
--- /dev/null
+++ b/面向对象学生系统/bll/update_student_partial.py
@@ -0,0 +1,4 @@
+def update_student_partial(self,sid:str,name:Optional[str]=None,height:Optional[int]=None,birth_date:Optional[date]=None,enrollment_date:Optional[date]=None,class_name:Optional[str]=None)->bool:
+    if not self.dal.check_student_exists(sid):
+        raise ValueError(f"学生ID{sid}不存在。")
+    return self.dal.update_student_partial(sid,name,height,birth_date,enrollment_date,class_name)
\ No newline at end of file