Objective:To observe the expression of interleukin 22(IL-22), interleukin 22 receptor 1(IL-22R1) and signaling and transcriptional activation factor 3(STAT3) in the different stages of malignant transformation of gastric cancer, and to illustrate the effect of IL-22 in the process. Methods:The tissues from patients with chronic gastritis (15 cases),gastric precancerous lesions(15 cases) and gastric carcinoma (15 cases) were collected and examined for IL-22,IL-22R1 and p-STAT3 expression by immunohistochemistry and real-time PCR. Results:Immunohistochemical analysis showed that IL-22 was mainly located in the cytoplasm of gastric epithelial cells and infiltrated immune cells. IL-22R1 was mainly expressed in the cytoplasm of gastric epithelial cells, while the location of p-STAT3 was mainly in the nucleus of gastric epithelial cells. The expression of IL-22, IL-22R1 and p-STAT3 in precancerous lesions and gastric carcinoma were significantly more than that in chronic gastritis. At the same time, IL-22,IL-22R1 and p-STAT3 were significantly increased in gastric carcinoma compared with precancerous lesions(P < 0.001). The expression of IL-22 and IL-22R1 mRNA were higher in precancerous lesions and gastric carcinoma than in chronic gastritis, and were higher in gastric carcinoma than in precancerous lesions(P < 0.05). Conclusion:In the cells of precancerous lesions and gastric carcinoma,IL-22 can be secreted by infiltrated immune cells and can also be self-secreted by atypical glandular epithelium.