Student participation, as a significant indicator of class learning, has been investigated from various perspectives. The present research seeks to explore student participation by drawing on text data from the chat box of an online learning platform. The two main research questions concern the main types of student participation indicated by the online chat data as well as how extensively and frequently students had participated online in class. The written text messages of 84 university students in the chat box were recorded in an online English course for three months in consecutives. The findings revealed that students' online chat data generally fell into five major types: students' responses of factual information (62.77%) social interaction (15.74%), phatic communication (9.95%), tech-related messages (7.5%) and class schedule (4.5%). With 89% of participation concerning meaningful interactions and 11% of participation dealing with simple clarification of tech problems and class schedules, the findings suggest a highly active and meaningful online in-class participation. In addition, further descriptive statistics depicted the level of participation in terms of its frequency and breadth. Results showed that the active and meaningful online participation had been persistent over three months with an average of 74.52% regular participating students and average 410 chat messages sent one day. Implications were discussed in relation to the features of student participation.