Objective To study the expression of adenomatous polyposis coli (APC) protein in primary gastric lymphoma (PGL) tissue, and explore its relationships with clinicopathological features, as well as the role of APC protein in the development and progress of PGL. Methods The clinical and pathological data of 45 patients with PGL admitted in Xiangya Hospital and Shaoyang Chinese Medicine Hospital between June 2006 and December 2011 were collected. The expression of APC protein in 45 cases of PGL and 30 samples of normal gastric mucosa tissue was studied with immunohistochemical staining (SP). Results The positive expression rate of APC protein was 37.78% in the PGL tissues and 90.00% in the normal gastric mucosa tissue, there was a significant difference (P < 0.05). There was no significant difference in the positive expression rate of APC protein among the patients with different genders, age or gross tumor morphology (P > 0.05). The positive expression rate of APC protein was correlated with clinical stage and lymph node metastasis (P < 0.05). Conclusions The APC protein is lowly expressed in PGL, and it plays an important role in the tumorigenesis of PGL, and may be an important potential predictor of tumorigenesis in PGL.