Objective To explore the effects of online formative assessment applied in Medical Nursing. Methods Forty students of Grade 2016 were enrolled as the control group. Formative assessment in the control group included performance in the class,homework,and practical assessment. Forty-seven students of Grade 2017 were recruited as the experimental group. Based on the online learning platform,the formative assessment was designed and implemented. The formative assessment in the experimental group included the number of platform visits,online self-learning,performance in the class,online learning activities involvement,and online examination. Results The total number of online platform visits was 13 576 for the experimental group. The completion rates of video learning and document learning were 46% and 35% respectively. The rates of class participation and online group mutual evaluation were 68% and 19%,respectively. The completion rates of online assessment were 79% and 95% respectively. There was no significant difference in the examination scores of Medical Nursing between the experimental group（69.81±13.23） and the control group（71.12±4.85）at the end of the first semester. The score of Medical Nursing in the experimental group（81.38±3.96） was better than that of the control group（71.63±5.09） at the end of the second semester（P<0.05）. Conclusion The online formative assessment is more comprehensive and objective. It is conducive to promoting students’ interest in learning. However,the construction and updating of online learning resource,the limitation of the network environment and the insufficiency of students’ autonomous learning ability are the limitations.