Objective To implement a Wechat-based continuing medical education system (Wechat-based CMES) for health-care workers (HCWs) in grass-roots control and prevention for COVID-19 and evaluate its effectiveness.Methods Five types of e-courses were designed and uploaded to the system. Data for learning and passing quizzes of HCWs who actively logged in the system with Wechat accounts from Feb 19th to Mar 5th, 2020 was collected and analyzed by chi square test, non-parametric test and logistic regression. The actual cost of the Wechat-based CMES was compared to the estimated cost of the on-site CME as well.Results The person time of HCWs who participated in studying e-courses and passed the quizzes were 26 939 and 52 784 respectively. The comment from HCWs on the e-courses was mainly “practical”. HCWs spent 96 minutes by an accumulate time for learning, reviewing and passing the quizzes using the Wechat-based CMES, however, they would have to spend 480 minutes for the same learning and passing the quizzes using the on-site CME.The full mark rate of quizzes of the 5 types of courses is 42.3% (22 309/52 748). Of the five courses,the course “field epidemiological investigation” has the highest full mark rate of 47.3% (5 869/12 421), the most learners of 12 421 person times and the longest exam time of 4.8 minutes per person time.Logistic regression shows that both quiz types and quiz time have effect on the full mark rate. The costs of on-site CME(4.73 thousand) was 47.6 times than that of the wechat-based CMES(0.996 thousand).Conclusions The use of Wechat-based CMES helps HCWs to learn actively and master the training content through repeated study and examination. Compared with the on-site CME, the Wechat-based CMES is more cost-effective.