Objective To investigate the cognitive understanding of medical college students on statistical indicators and statistical charts, and to examine the effect of online testing tools on improving students′ ability to understand statistical charts.Methods The subjects were undergraduates majoring in statistics, clinical medicine, anesthesiology, imaging and laboratory science in a medical university. The survey was conducted by online questionnaire (questionnaire url, test one: https://ks.wjx.top/jq/92107364.aspx, test two: https://ks.wjx.top/jq/92106453.aspx). Frequency, rate and mean were used to describe qualitative and quantitative data. Quantitative data were compared by paired- t- test or rank sum test.Results Five hundred and forty-six students completed test one and 476 completed test two. We found that quite a few students were wrong about basic statistical charts. And 70% of medical students misunderstood the composition ratio of the two grouping factors, while 50% of medical students misunderstood the constituent ratio of a grouping factor. Between 30% and 50% of medical students misunderstood the rate, the difference between case mortality and mortality, and the correlation shown in the scatter plot.Conclusion If statistical charts can only be understood and mastered by classroom explanation， due to the limitation of class hours, the goal of accurate understanding can not be achieved. Through online testing and cases, combined with answer analysis, this part of knowledge can be mastered in a limited period of time. If students only understand and master statistical charts through classroom explanation, they cannot achieve the goal of accurate understanding due to the limitation of class hours. In the ways of online tests and the design of cases and questions, combined with the way of answer analysis, can students master this part of knowledge in a limited period of time.