(1) Background: Pre-service physical education teachers commonly embrace social media for multiple purposes. However, little is known about their perception of social media, which could affect the appropriate use of social media in their future professional work. This study aims to explore a theoretical model of how pre-service physical education teachers perceive social media in order to provide a basis for educators to guide their appropriate use of social media. (2) Methods: Qualitative data were collected in diverse ways, mainly from interviews. Seventeen Chinese preservice physical education teachers were selected as participants by a purposive sampling technique. The interview questions focused on participants’ motivation, expectations, and experiences in social media usage. Grounded theory was used to analyze the data by ROST CM and Nvivo 12. (3) Results: The perception of social media among teachers includes three subsidiary categories made up of 10 sub-categories, 70 concepts, and 307 labels. The three categories are (a) value perception, including the perspective of intelligent function, interaction, and rich information, (b) risk perception, involving psychological risk, information risk and privacy risk and (c) overall perception, like development trends, current status and basic elements. (4) Conclusions: Chinese preservice physical education teachers perceive social media as having similarities and differences compared to other countries. Future research should consider a large sample survey to revise and verify the initial exploration of perception and study diverse groups of teachers’ perceptions of social media.