Objective:To observe the clinical efficacy of Weikangning prescription in the treatment of chronic atrophic gastritis (CAG) of spleen deficiency and cold-heat stagnation pattern accompanied with precancerous lesion of gastric carcinoma (PLGC)and regulation mechanism on COX-2 protein. MethodsNinety cases with CAG of spleen deficiency and cold-heat stagnation pattern accompanied with PLGC were randomly divided into the treatment group and control group,45 cases in each group.The treatment group was orally treated with Weikangning prescription and the control group was orally treated with Weifuchun tablets,with a course of 12 weeks.The clinical efficacy and pathological changes were observed and the changes of TCM syndrome scores and COX-2 protein in gastric mucosa were compared between the two groups.  Results:① The total effective rate in the treatment group and control group was 93.3% and 57.6% respectively；there was statistically significant difference on the clinical efficacy between the two groups (P<0.05).②Comparison of treatment before and after,there were statistically significant differences on the inflammation, atrophy,intestinal metaplasia and total score in both groups (P<0.05). Comparison between the two groups,there were statistically significant differenceson the inflammation, atrophy,intestinal metaplasia and total score after treatment (P<0.05).③Comparison of treatment before and after,there were statistically significant differences on the stomach pain, abdominal fullness, noisy, fatigue, anorexia andtotal score in both groups (P<0.05). Comparison between the two groups,there were statistically significant differences on the stomach pain, abdominal fullness, anorexia andtotal score after treatment (P<0.05).④Comparison of treatment before and after,there was statistically significant difference on the COX-2 in the treatment group (P<0.05). Comparison between the two groups,there was statistically significant difference on the COX-2 after treatment (P<0.05).  Conclusion:Weikangning prescription shows good effects in the treatment of chronic atrophic gastritis with precancerous lesions of spleen deficiency and cool heat stagnation pattern,which significantly improve the clinical symptoms of patients,relieve inflammation in gastric mucosa and reverse gastric mucosal atrophy and intestinal metaplasia. Reducing the protein expression of COX-2 in gastric mucosa may be one of the mechanisms.