C-erbB-2 is a cancer gene originating from cells. The high-expression and amplification of C-erbB-2 and its protein products (P185) are found in a wide variety of tumors. The abnormal expression of C-erbB-2 has great influence on the occurrence and development of gastric carcinoma. This paper aimed to analyze the expression of C-erbB-2 in the tissues of gastric carcinoma, gastric mucosal atypical hyperplasia and gastritis, and discuss its role in the occurrence and development of gastric carcinoma. The morphological differences and connections among simple intestinal metaplasia (SIM), atypical intestinal metaplasia (AIM) and dysplasia in intestinal metaplasia through hematoxylin and eosin (HE) staining were studied. Three groups were set to detect the expression condition of C-erbB-2 by immunohistochemical method (IHC). The result showed that C-erbB-2 had no significant difference in AIM and gastric carcinoma, that is, AIM was closely related to gastric carcinoma. The positive expression was demonstrated of C-erbB-2 products (P185) in medium and gastric mucosa dysplasia tissues and was 29.41% and 66.67%, respectively, while it was 25%, 50% and 77.78% in high, medium and low differentiation of gastric carcinoma. It can be seen that there was a significant difference between them (P<0.05), and the expression degree was significantly enhanced (P<0.05); the expression degree in high differentiation gastric cancer tissue was significantly higher than the middle and low differentiation gastric cancer tissue. It was concluded that C-erbB-2 played an important role in the pathogenic mechanism of gastric carcinoma, and it might act on the later period of the gastric carcinoma, which provides objective reference index for the diagnosis and prognosis of gastric carcinoma and meanwhile provides instructional theoretical reference for the application of targeted drugs in the clinical treatment of gastric carcinoma.