Objective:To detect expression of BRCA1 in colorectal polypiod lesions,and find its clinical significance in different pit patterns. Methods:According to Kudo criteria, pit patterns observed by magnifying chromoendoscopy include I~V type,nonneoplastic lesion(Ⅰ~Ⅱtype),adenomas lesion(ⅢL~Ⅳ type) and cancer lesion(Ⅴtype). All samples diagnosises were proved by pathological examination. Biopsy specimens were used to detect expression of BRCA1 proteins by SP immunohistochemical method. Results:Total 256 polypoid lesions were observed by magnifying chromoendoscopy. The positive expressions of BRCA1 increased gradually from typeⅠto typeⅤ,and there were statistical significances between every two groups(P < 0.000 1); The positive expresion of BRCA1 protein in cancer lesions was significantly higher than that in adenomas lesions and nonneoplastic lesions(P < 0.000 1). Conclusion:The positive rate of BRCA1 protein expression gradually increased in different pit patterns,especially in cancer lesions diagnosed by magnifying chromoendoscope. It was helpful to find early colorectal cancer by the detection of the BRCA1 protein expression in colorectal lesions combined with magnifying chromoendoscope.