With the rapid development of network information technology, the channels for the public to obtain scientific knowledge have changed. Short video platforms represented by Tik Tok are playing an increasingly important role in science popularization. There are huge differences among the communication effects of various science popularization short videos on Tik Tok. Therefore, it’s meaningful to introduce “communication capacity” as an index to measure video’s communication effect and investigate the influencing factors. This paper quantifies the communication capacity based on the entropy method. 100 science popularization short videos ranking at the top on Tik Tok between November 1st 2019 and Feburary 1st 2020 were examined to find their common characteristics of high communication capacity. In the light of characteristics of top science popularization videos, it is recommended to produce high-quality content adapted to target platform, develop personalized science popularization accounts and increase user engagement.