【Abstract】 Objective To explore the relationship between MiR203 promoter methylation and Barrett esophagus cancerous. Methods RTPCR detected the expression level of miRNA203 in Barrett esophagus, esophageal cancer and normal esophageal mucosa cells, before and after demethylation processing. MiR203 promoter methylation level was measured by MSP. Immunohistochemistry was used to test the expression and distribution of KRas, a target of miR203 in esophageal cancer, BE and normal esophagus tissues. Results MiR203 expressions levels were reduced obviously in Barrett esophagus and esophageal cancer cells than normal esophageal cells (P=0003). After demethylation treatment, miR203 expressions are significantly increased in Barrett's esophagus and esophageal cancer cells, the differences are statistically significant (P=003). MSP showed miR203 promoter changes to be lowmethylation or nonmethylation.Conclusion MiR203 in Barrett's esophagus and esophageal cancer cells reduced expression is related to its Promoter methylation, miR203 promoter methylation throughout the carcinogenesis of Barrett's esophagus, it may become a key molecular biomarker in process of Barrett esophagus cancerous, and may become the prevention and treatment targets of Barrett esophagus cancerous.