Rain Classroom, as a mobile app designed and developed by Tsinghua University, has been catching increasingly intense attention since her birth in 2016. Her usability has, however, seldom been explored. The purpose of this study is to compare the usability of Rain Classroom assisted learning with other learning approaches. A mixed design was adopted to collect both quantitative and qualitative data. Via pre- and post-questionnaires, we collected quantitative data. Through analyzing the data, we concluded that the usability of Rain Classroom was significantly higher than that of the traditional learning in terms of eight attributes: effectiveness, efficiency, satisfaction, learnability, memorability, errors, cognitive load and timeliness. Via the semi-structured interviews, we collected qualitative data, based on which the findings are generally consistent with those from questionnaires. Future research may focus on development of more advanced mobile apps, between which the usability comparison may be conducted assisted with interdisciplinary cooperation such as statistics, education, psychology and computer technology.