Abstract: Optimized screening protocol for colorectal cancer contained RPHA-FOBT and risk factor screening，higher-risk population was defined as individuals with a positive RPHA-FOBT test，or with family history of colorectal cancer in first degree relatives，or with personal history of malignant tumours，or with two or more of following five indicators:(a) mucous and bloody stool;(b)chronic diarrhea;(c) chronic constipitation;(d)history of chronic appedicatis;(e)history of psychic trauma. To evaluate optimized screening protocol for colorectal cancer，A screening study was conducted among the high-incidence population in Raining Zhejiang province in 1993.1722 cases were enrolled，most of them with history of colorecta polyps·Each subject had 60cm flexible sigmoidoscopy examination，Results of sigmoidoscopy examination were considered as criteria.It was shown that the effectiveness of screening for colorectal cancer was satisfactory，and the protocol was convenient and promising.