diff --git a/apps/wpm/migrations/0048_alter_stlog_sflog.py b/apps/wpm/migrations/0048_alter_stlog_sflog.py
new file mode 100644
index 00000000..cd7320cf
--- /dev/null
+++ b/apps/wpm/migrations/0048_alter_stlog_sflog.py
@@ -0,0 +1,19 @@
+# Generated by Django 3.2.12 on 2024-05-21 10:17
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('wpm', '0047_alter_sflogexp_unique_together'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='stlog',
+            name='sflog',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL, to='wpm.sflog', verbose_name='发生时所在值班'),
+        ),
+    ]
diff --git a/apps/wpm/models.py b/apps/wpm/models.py
index 19172b93..0d888265 100644
--- a/apps/wpm/models.py
+++ b/apps/wpm/models.py
@@ -54,7 +54,7 @@ class StLog(CommonADModel):
     mgroup = models.ForeignKey(
         Mgroup, verbose_name='关联工段', on_delete=models.CASCADE)
     sflog = models.ForeignKey(
-        SfLog, on_delete=models.CASCADE, verbose_name='发生时所在值班', null=True, blank=True)
+        SfLog, on_delete=models.SET_NULL, verbose_name='发生时所在值班', null=True, blank=True)
     sflogs = models.ManyToManyField(
         'wpm.sflog', verbose_name='关联所有当班', through='wpm.sflogexp', related_name='stlog_sflogs')
     start_time = models.DateTimeField('发生时间')