diff --git a/backend/tests/test_import_validation.py b/backend/tests/test_import_validation.py
new file mode 100644
index 0000000..19487d9
--- /dev/null
+++ b/backend/tests/test_import_validation.py
@@ -0,0 +1,36 @@
+import pytest
+from pydantic import ValidationError
+
+from wisegrade.api import ImportConfirm, ProjectConfirm
+
+
+def project(**changes):
+    return {"relative_dir": "test/student", "student_no": "9000000001", "name": "学生甲", "topic": "机器人项目",
+            "files": [{"relative_path": "test/student/最终报告.pdf", "category": "final_report", "sha256": "a" * 64}], **changes}
+
+
+def test_confirm_normalizes_identity_before_validating():
+    result = ProjectConfirm.model_validate(project(student_no=" 9000000001 ", name=" 学生甲 ", topic=" 机器人项目 "))
+    assert (result.student_no, result.name, result.topic) == ("9000000001", "学生甲", "机器人项目")
+
+
+@pytest.mark.parametrize("changes", [
+    {"name": "   "}, {"topic": "   "}, {"student_no": "９００００００００１"}, {"files": []},
+    {"files": [{"relative_path": "test/student/a.pdf", "category": "unknown", "sha256": "a" * 64}]},
+    {"files": [{"relative_path": "test/student/a.pdf", "category": "final_report", "sha256": "a" * 64, "status": "ignored"}]},
+    {"files": [{"relative_path": f"test/student/{i}.pdf", "category": "final_report", "sha256": "a" * 64} for i in range(2)]},
+])
+def test_confirm_rejects_invalid_identity_or_selection(changes):
+    with pytest.raises(ValidationError):
+        ProjectConfirm.model_validate(project(**changes))
+
+
+def test_empty_import_is_rejected():
+    with pytest.raises(ValidationError):
+        ImportConfirm(course_version_id=1, projects=[])
+
+
+def test_ignored_unknown_material_does_not_block_valid_selection():
+    data = project()
+    data["files"].append({"relative_path": "test/student/foreign.pdf", "category": "unknown", "sha256": "b" * 64, "status": "ignored"})
+    assert len(ProjectConfirm.model_validate(data).files) == 2
diff --git a/backend/wisegrade/api.py b/backend/wisegrade/api.py
index 0c65344..0a23666 100644
--- a/backend/wisegrade/api.py
+++ b/backend/wisegrade/api.py
@@ -3,7 +3,7 @@ from pathlib import Path
 
 from fastapi import APIRouter, Depends, HTTPException
 from fastapi.responses import FileResponse
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, field_validator, model_validator
 from sqlalchemy import func, select
 from sqlalchemy.orm import Session
 
@@ -67,16 +67,33 @@ class FileConfirm(BaseModel):
 
 class ProjectConfirm(BaseModel):
     relative_dir: str
-    student_no: str = Field(pattern=r"^\d{5,20}$")
+    student_no: str = Field(pattern=r"^[0-9]{5,20}$")
     name: str = Field(min_length=1)
     topic: str = Field(min_length=1)
     direction: str = ""
-    files: list[FileConfirm]
+    files: list[FileConfirm] = Field(min_length=1)
+
+    @field_validator("student_no", "name", "topic", "direction", mode="before")
+    @classmethod
+    def trim_identity(cls, value):
+        return value.strip() if isinstance(value, str) else value
+
+    @model_validator(mode="after")
+    def validate_selection(self):
+        selected = [file for file in self.files if file.status != "ignored"]
+        if not selected:
+            raise ValueError("至少选择1份资料")
+        categories = [file.category for file in selected]
+        if any(category not in CATEGORIES for category in categories):
+            raise ValueError("请选择有效材料类型")
+        if len(set(categories)) != len(categories):
+            raise ValueError("每类材料只允许选择1份，其余请设为忽略")
+        return self
 
 
 class ImportConfirm(BaseModel):
     course_version_id: int
-    projects: list[ProjectConfirm]
+    projects: list[ProjectConfirm] = Field(min_length=1)
 
 
 class BatchInput(BaseModel):