Objective：To explore the relationship between margin width in extended lumpectomy for breast cancer with survival rate, local recurrence rate,and cosmetic result.Methods: The clinical data of 42 breast cancer patients who had a 2 cm incision margin width (group A) and 37 who had a 3cm incision margin width (group B) were retrospectively analyzed. The 5year, 10year survival rates, recurrence rates, and the cosmetic results were compared between the 2 groups. Results: The 5year and 10year survival rates in patients of group A were 90.1% and 85.3%, respectively; in patients of group B were 92.3% and 83.6%, respectively（P>0.05）. The 5year and 10year local recurrence rates in patients of group A were 5.9% and 11.6%, respectively; in patients of group B were 3.4% and 12.9%, respectively（P>0.05）.The cosmetic result was significantly better in group A than that in group B（P<0.05）.Conclusion: An incision margin width of 2 cm is enough for extended lumpectomy. It is not necessary to further expand the margin width; otherwise, it may influence the cosmetic results after operation.