Objective:To explore the reform practice and teaching effect of flipped classroom combined with case-based learning (CBL) in the undergraduate teaching of International Classification of Diseases.Methods:The undergraduates of Chongqing Medical University majoring in information management and information system from the classes of 2018 and 2019 were selected as the control group and the experimental group, respectively, and the undergraduates in the control group received lecture-based learning, while those in the experimental group received flipped classroom combined with CBL. After teaching, theoretical assessment and practical skill assessment were performed to evaluate learning effect. R3.6.3 was used to perform statistical analyses; the t-test or the rank-sum test (Mann-Whitney U test) was used for comparison of continuous data between groups, and the chi-square test was used for comparison of categorical data. Results:There were no significant differences between the two groups in the general information such as age and sex distribution ( t=-1.22, P=0.227; χ2=1.77, P=0.183). There was no significant difference in theoretical assessment score between the two groups [(78.84±8.97) vs. (76.01±8.65), P=0.140]. Compared with the control group, the experimental group had significantly better results in the correct rate of ICD coding [(94.34±3.22)% vs. (91.36±2.79)%, P=0.006] and the number of coded copies per person per day [15.41 (7.90, 40.97) vs. 7.22 (2.33, 8.83), P=0.006], as well as a better level of practical skills. Conclusions:Flipped classroom combined with CBL can help to enhance the hands-on ability to solve problems among students, thereby improving the overall teaching effect.