Objective To evaluate the changes in oral health knowledge, behavior and attitude of undergraduate students majoring in preventive medicine before and after the course “Oral Preventive Medicine”, and to provide empirical evidence for the teaching reform of preventive medicine undergraduate programs, thereby enhancing teaching effectiveness and the significance of the course. Methods A questionnaire survey was conducted among the undergraduate students majoring in preventive medicine at the West China School of Public Health, Sichuan University in 2024, before and after the compulsory course “Oral Preventive Medicine”. Results A total of 124 undergraduate students majoring in preventive medicine were surveyed. After the course, undergraduate students majoring in preventive medicine had changed their oral related knowledge, behaviors, and attitudes. The correctness of the answers and the usage rate of Bass brushing technique were both increased; The self-evaluation of oral health status (χ2=5.017, P=0.025) and brushing effect (χ2=22.200, P<0.001) were both improved; The perceived benefits of brushing (t=2.515, P=0.013) and behavioral intention to brush teeth (t=5.381, P<0.001) were both improved, while the perceived barriers to brushing was reduced (t=−3.999, P<0.001). Conclusions The course “Oral Preventive Medicine” effectively enhanced the oral health literacy of undergraduate students majoring in preventive medicine, confirming its practical value in undergraduate teaching reform. It provides an important reference for optimizing the curriculum system of preventive medicine, has positive significance for cultivating public health talents with comprehensive health literacy.