Objective To design and develop a colorectal cancer early screening assistant platform based on WeChat applet to improve residents' compliance with colorectal cancer (CRC) screening and improve the work efficiency of medical staff. Methods The front-end WeChat applet was developed based on WeChat applet Markup Language (PHP), and the back-end cloud server was developed based on the SpringBoot framework. The front-end and back-end data transmission follows the JavaScript object representation (JSON) format to complete the design and development of the platform. Results The platform has the functions of questionnaire filling, fecal occult blood results evaluation, screening data collection and analysis, screening results feedback and health education. In the past three years since the operation of the platform, 25,192 people have visited the early screening assistant platform and filled in the online CRC screening questionnaire, 20,457 people have received colloidal gold method of FOBT paper, and 1,321 people have completed colonoscopy according to the suggestions of specialists. Compared with the urban cancer  screening results in Chongqing from 2012 to 2016, the patients who underwent CRC screening through this platform had higher compliance, higher lesion detection rate, and higher detection rate of polyps and hemorrhoids, adenoma and adenocarcinoma (P＜0.05). Conclusion The early screening assistant platform based on WeChat applet is convenient for publicity, popularization, and the users' operation, which can effectively improve the compliance of residents with CRC screening and improve the work efficiency of medical staff.