diff --git a/sf_plan/models/custom_plan.py b/sf_plan/models/custom_plan.py
index 03117a3a..96e98773 100644
--- a/sf_plan/models/custom_plan.py
+++ b/sf_plan/models/custom_plan.py
@@ -220,7 +220,7 @@ class sf_production_plan(models.Model):
         """
         sequence = workorder_id_list.index(item.id) - 1
         # 计算CNC加工之前工单的开始结束时间
-        for i in range(sequence):
+        for i in range(1 if sequence == 0 else sequence):
             current_workorder_id = (item.id - (i + 1))
             current_workorder_obj = self.env['mrp.workorder'].sudo().search(
                 [('id', '=', current_workorder_id)])