Objective To explore the influence mechanisms of classroom learning effect among medical undergraduates, and to provide basis for improving their classroom performance. Methods By using the questionnaire survey method, a cluster sampling survey was conducted among 567 medical undergraduates in Anhui Medical University from April to June 2023. The questionnaire was designed based on the improved information-motivation-behavioral skills model. The structural equation model was used to analyze the influence paths of classroom learning effect, and the Bootstrap method was employed to test the mediating effect of learning skills. Results The score of classroom learning effect among medical undergraduates was 10.95±2.10. The scores of the influencing factors, namely information reserve, learning motivation, learning skills and external environment, were 8.36±1.49, 12.94±2.90, 14.82±2.81 and 10.04±2.22, respectively. The results of the structural equation model showed that the path coefficients from information reserve, learning motivation and learning skills to classroom learning effect were 0.206, 0.392 and 0.344 respectively (all P<0.05), while the path coefficient of the external environment was 0.117 (P>0.05). The four variables could jointly explain 79.2% of the variance in classroom learning effect. The mediating effect of learning skills between information reserve and learning effect accounted for 46.7%, and between learning motivation and learning effect accounted for 23.6% (all Z>1.96). Conclusions The classroom learning effect among medical undergraduates was significantly positively influenced by information reserve, learning motivation and learning skills, while the positive influence of the external environment was not obvious. Learning skills played a mediating role between information reserves and learning effect, as well as between learning motivation and learning effect. The classroom teaching should focus on stimulating medical undergraduates' learning motivation, enriching their information reserves, cultivating their learning skills, and ensuring a supportive learning environment, to improve the classroom learning effect among medical undergraduates.