Although online learning has been widely used in higher education, its impact on students' academic performance has not been well described. This study surveyed 2963 college students, and used structural equation modelling to determine the impact of college students' online learning engagement on academic performance. The serial mediating effect of inquiry learning and reflective learning on the relation between online learning engagement and academic performance was also investigated. Results indicated that online learning engagement could positively predict college students' academic performance. Inquiry learning and reflective learning had a serial mediating effect on the relationship between online learning engagement and academic performance. Reflective learning played a complete mediating role in the relation between inquiry learning and academic performance. This suggests that college students' online academic performance can be improved by promoting their online learning engagement and encouraging them to use inquiry learning and reflective learning strategies.