To evaluate the effectiveness of an all-English small class inquiry-based teaching model for basic theories and practices in epidemiology, providing a reference for further improving the quality of all-English instruction in preventive medicine courses.

Based on the undergraduate course “Basic Theory and Case Study of Epidemiology” at Sichuan University, surveys were conducted before and after the course for students in both small and large all-English classes.A comparative analysis was performed between the two class sizes and within the same class before and after the intervention to explore whether the small class inquiry-based teaching model is more advantageous than traditional large class teaching in enhancing students’ all-English professional competence.

Prior to the all-English instruction, there were significant differences in English reading and writing abilities, as well as listening and speaking skills, between students in large and small classes, with small class students demonstrating superior skills (reading and writing: small class 57.1% vs. large class 26.8%;listening and speaking: small class 50.0% vs. large class 20.5%) (P<0.05). Most students in both class sizes lacked experience in delivering presentations and writing research papers in English before the instruction; however, small class students were more willing to attempt all-English oral presentations in class compared to their large class counterparts (small class 92.9% vs.large class 60.7%) (P<0.05). Following the all-English instruction, a significant improvement was observed in English reading and writing abilities, professional knowledge, mastery of English terminology, and participation in group discussions or projects for students in both classes. Overall, small class students exhibited better listening and speaking skills than those in large classes post-instruction, with 50.0% of small class students demonstrating good English listening and speaking skills compared to 14.1% in large classes, reflecting an overall improvement from pre-instruction levels. Small class students reported increased confidence in writing English research papers and more experiences with all-English presentations compared to large class students. Moreover, over 60% of students from both classes expressed a willingness to participate in international conferences and deliver all-English presentations, showing an increase from pre-instruction levels.

The all-English small class inquiry-based teaching model demonstrates greater advantages over large class teaching in enhancing students’ all-English professional competence, contributing to improved international competitiveness for employment and further studies.Implementing this model for undergraduate students in preventive medicine is both feasible and effective.