[Purpose/significance] Synchronous online courses are widely adopted as an important method in online education. In order to improve the teaching quality and increase students’ satisfaction in synchronous online courses, this paper based on the transactional distance theory, explored the mechanism of the impact of dialogue, structure and interaction distance on student satisfaction in synchronous online courses, and whether the different course types would lead to different results. [Method/process] For an empirical test of our research model, we collected data from individuals via online channels. Our questionnaires were distributed to students from Wuhan University and other universities. [Result/conclusion]The results show that in synchronous online courses, dialogue and structure both have a significant impact on satisfaction. Among them, the interaction distance plays a partial mediating role between dialogue and satisfaction, and the course types play a moderating role in the relationship between dialogue and interaction distance. Therefore, designers and teachers of online learning platforms should pay attention to the importance of interaction in the dimension of dialogue and structure. Platform designers should promote the user's use of interactive functions by enhancing the convenience and flexibility of using interactive functions in the platform. Teachers should consciously strengthen interactions in the course. At the same time, they should also focus on the development of two interactions in the dialogue dimension in different types of online courses.