【Abstract】 Objective To explore the relationship between MiR145 promoter methylation and gastric polyps cancerous. Methods RTPCR detected the expression levels of miRNA145 in gastric polyps, gastric adenocarcinoma cancer and normal gastric tissues. MiR145 promoter methylation levels were measured by MSP. Immunohistochemistry was used to detect protein Mucin expression levels in gastric polyps, gastric adenocarcinoma cancer and adjacent normal gastric tissues. Results MiR145 expression levels were reduced obviously in gastric polyps and gastric adenocarcinoma than normal gastric tissues, the difference was statistically significantly. Protein Mucin expression levels in gastric polyps and gastric adenocarcinoma were lower than normal gastric tissues, and it was lower in gastric adenocarcinoma than gastric polyps. MSP showed highmethylation in miR145 promoter in gastric polyps and gastric adenocarcinoma. Conclusion MiR145 expression levels in gastric polyps and adenocarcinoma were lower than normal gastric tissues, it may be caused by highmethylation in miR145 promoter, and it may become a key molecular biomarker in the process of gastric cancerous.