The Carbon Generalized System of Preferences(CGSP) is an innovative carbon reduction policy which focuses on individuals and is important for promoting carbon neutrality at the individual level. However, most of the CGSP practice projects led by local governments and enterprises have low participation. Therefore, taking Ant Forest, a CGSP project with the most successful operation model, as an example, an LDA topic model was constructed to explore users' motivation for participation based on Sina Weibo blog data. The results show that the topics of users’ concern can be divided into four categories,and it is further extracted that the users’ participation behavior is driven by hedonic motivation, benefit motivation and normative motivation combined with the goal framework theory.The psychological mechanism behind the user participation behavior is revealed, so as to provide reference for other CGSP projects.