Purpose To study the clinicopathologic features and differential diagnosis of serous microcystic adenoma of pancreas ( SMAP) . Methods Immunohistochemical study was carried out, and the clinical and pathologic features were evaluated in 11 cases of SMAP, and review the literatures. Results The age of onset of 11 cases of SMAP ranged from 41~68 years ( average=55 years) . All of them were females. The clinical presentations were right upper abdominal pain, nausea, vomiting and weight loss. Five tumors located in the pancreas head (45. 5%). Grossly, ten cases were solitary, one case was multiple. The boundary of tumor was clear, the cut surface of tumor was honeycomb. Histologic examination showed that the tumors were made up of small sized capsule wall lining of single-layer flat or cube epithelial cell. The cytoplasm was clear, nucleus was small and no atypical features. Immunohistochemical study showed that all of the 11 cases were positive for CK, CK7, CK18, CK19, EMA, 3 cases were positive for NSE,α-ACT, all of the 11 cases were negative for CgA, Syn, vimentin, TG, Calretinin. Ki-67<1%. Vascular vessels were positive for D2-40 and CD34. Conclusions SMAP is a very rare benign tumor of pancreas. It should be distinguished from oligo-cystic cystadenoma, pseudocyst, mucinous cystadenoma, lymphangioma and capillary hemangioma, mesothelioma.