diff --git a/apps/wpm/filters.py b/apps/wpm/filters.py
index 68772d9f..705ef4f6 100644
--- a/apps/wpm/filters.py
+++ b/apps/wpm/filters.py
@@ -132,7 +132,8 @@ class WMaterialFilter(filters.FilterSet):
             "notok_sign": ["exact", "in", "isnull"],
             "count_xtest": ["gte", "isnull"],
             "supplier": ["exact"],
-            "defect": ["exact", "isnull"]
+            "defect": ["exact", "isnull"],
+            "defect__okcate": ["exact", "in"],
         }
 
 class MlogFilter(filters.FilterSet):
diff --git a/apps/wpm/serializers.py b/apps/wpm/serializers.py
index 7b53df64..c01dae8c 100644
--- a/apps/wpm/serializers.py
+++ b/apps/wpm/serializers.py
@@ -190,12 +190,20 @@ class WMaterialSerializer(CustomModelSerializer):
     notok_sign_name = serializers.SerializerMethodField()
     defect_name = serializers.CharField(source="defect.name", read_only=True)
     defect_okcate = serializers.IntegerField(source="defect.okcate", read_only=True)
+    defect_grade = serializers.SerializerMethodField()
+    defect_grade_name = serializers.SerializerMethodField()
     count_working = serializers.SerializerMethodField(label='在制数量')
     count_handovering = serializers.SerializerMethodField(label='正在交送的数量')
 
     def get_notok_sign_name(self, obj):
         return getattr(NotOkOption, obj.notok_sign, NotOkOption.qt).label if obj.notok_sign else None
 
+    def get_defect_grade(self, obj):
+        return obj.defect.okcate if obj.defect else None
+
+    def get_defect_grade_name(self, obj):
+        return obj.defect.get_okcate_display() if obj.defect else None
+
     def get_count_working(self, obj):
         # 列表接口 queryset 已注解(单次聚合); 嵌套等无注解场景回退模型属性
         # 保留 decimal 精度(原 IntegerField 会截断在途量, 导致可用/可交接量偏大)
diff --git a/apps/wpm/tests.py b/apps/wpm/tests.py
index 22a10353..189faf9e 100644
--- a/apps/wpm/tests.py
+++ b/apps/wpm/tests.py
@@ -13,7 +13,11 @@ from apps.qm.models import Defect
 from apps.system.models import Dept, User
 from apps.wpm.filters import HandoverFilter, WMaterialFilter
 from apps.wpm.models import Handover, WMaterial
-from apps.wpm.serializers import HandoverSerializer, WMaterialCreateSerializer
+from apps.wpm.serializers import (
+    HandoverSerializer,
+    WMaterialCreateSerializer,
+    WMaterialSerializer,
+)
 from apps.wpm.services import restore_mlog_wpr_defects, snapshot_mlog_wpr_defects
 from apps.wpm.views import MlogbwViewSet
 from apps.wpmw.models import Wpr, WprDefect
@@ -100,6 +104,87 @@ class HandoverFilterTests(TestCase):
         ])
 
 
+class WMaterialDefectGradeTests(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        cls.material = Material.objects.create(name="缺陷等级测试物料")
+        cls.defect_b = Defect.objects.create(
+            name="B类缺陷",
+            cate=Defect.cate_list[0],
+            okcate=Defect.DEFECT_OK_B,
+        )
+        cls.defect_notok = Defect.objects.create(
+            name="不合格缺陷",
+            cate=Defect.cate_list[0],
+            okcate=Defect.DEFECT_NOTOK,
+        )
+        cls.normal_with_notok_defect = WMaterial.objects.create(
+            material=cls.material,
+            batch="NORMAL-NOTOK",
+            count=1,
+            state=WMaterial.WM_OK,
+            defect=cls.defect_notok,
+        )
+        cls.notok_with_b_defect = WMaterial.objects.create(
+            material=cls.material,
+            batch="NOTOK-B",
+            count=1,
+            state=WMaterial.WM_NOTOK,
+            defect=cls.defect_b,
+        )
+        cls.normal_without_defect = WMaterial.objects.create(
+            material=cls.material,
+            batch="NORMAL-NONE",
+            count=1,
+            state=WMaterial.WM_OK,
+        )
+
+    def test_serializer_exposes_nullable_defect_grade_without_using_state(self):
+        normal_notok_data = WMaterialSerializer(
+            self.normal_with_notok_defect
+        ).data
+        notok_b_data = WMaterialSerializer(self.notok_with_b_defect).data
+        no_defect_data = WMaterialSerializer(self.normal_without_defect).data
+
+        self.assertEqual(
+            normal_notok_data["defect_grade"], Defect.DEFECT_NOTOK
+        )
+        self.assertEqual(normal_notok_data["defect_grade_name"], "不合格")
+        self.assertEqual(
+            notok_b_data["defect_grade"], Defect.DEFECT_OK_B
+        )
+        self.assertEqual(notok_b_data["defect_grade_name"], "合格B类")
+        self.assertIsNone(no_defect_data["defect_grade"])
+        self.assertIsNone(no_defect_data["defect_grade_name"])
+
+    def test_filtering_state_and_defect_grade_are_independent(self):
+        normal_notok = WMaterialFilter(
+            {
+                "state": WMaterial.WM_OK,
+                "defect__okcate": Defect.DEFECT_NOTOK,
+            },
+            queryset=WMaterial.objects.all(),
+        ).qs
+        notok_b = WMaterialFilter(
+            {
+                "state": WMaterial.WM_NOTOK,
+                "defect__okcate": Defect.DEFECT_OK_B,
+            },
+            queryset=WMaterial.objects.all(),
+        ).qs
+
+        self.assertQuerySetEqual(
+            normal_notok,
+            [self.normal_with_notok_defect],
+            transform=lambda item: item,
+        )
+        self.assertQuerySetEqual(
+            notok_b,
+            [self.notok_with_b_defect],
+            transform=lambda item: item,
+        )
+
+
 class MlogbwViewSetTests(SimpleTestCase):
     @patch("apps.wpm.views.MlogViewSet.lock_and_check_can_update")
     @patch("apps.wpm.views.Mlogbw.cal_count_notok")