Drawing on the self-determination theory, this study explored the effect of three kinds of low-carbon knowledge (LCB), including system knowledge (SK), action-related knowledge (AK), and effectiveness knowledge (EK), on college students’ low-carbon behavior (LCB) by focusing on the mediating role of low-carbon intrinsic motivation (LCIM) and the moderating role of climate change risk perception (CCRP). Using a sample of 2846 college students in China, this study found that SK has an inverted U-shaped relationship with LCB, but AK and EK positively affect LCB. Moreover, LCIM mediates the relationship between three kinds of LCK and LCB. The moderated path analysis also indicated that CCRP could strengthen the impact of LCB on LCIM. Finally, this study discusses the theoretical significance of these findings and provides some policy suggestions and practical implications for the government.