ABSTRACT Mentor is an important leader of graduate learning and growth. Whether the mentor’s education and guidance are timely and accurate is the key to improve the quality of graduate education. Based on the social information processing theory and the learning engagement theory, this study constructed a research model with postgraduate research ability as the dependent variable, mentor support as the independent variable, research learning engagement and research self-efficacy as the mediating variables, and academic atmosphere as the moderating variable. Using SEM and Bootstrapping methods, this study conducted an empirical analysis on the multi-time point data of 641 graduate students collected through questionnaires from February 2023 to June 2023. The results show that the mentor support positively affects postgraduate research ability; Research self-efficacy and research learning engagement mediate the relationship between mentor support and postgraduate research ability; Academic atmosphere can not only moderate the direct effect of mentor support on research learning engagement and research self-efficacy, but also moderate the indirect effect of mentor support on postgraduate research ability through research learning engagement and research self-efficacy.