Objective: To understand the overall mental health status of freshmen in colleges and universities in Jiangsu Province, to investigate the effectiveness of mental health courses in improving the mental health of freshmen, so as to provide a reference for improving the mental health of freshmen. Methods: A total of 3 358 freshmen from a university in Jiangsu were selected from March to April 2019, mental health courses were held once(2 class hours each time) a week for 8 consecutive weeks,16 class hours in total(8 class hours of classroom teaching, and 8 class hours of experiential teaching). All the participants were used the Chinese College Students Mental Health Scale to conduct a questionnaire survey followed up before, during and after the implementation of mental health courses. Results: A total of 186 students with serious psychological problems were screened before the course, accounting for 5.54% of the total number, 310 students with general psychological problems, accounting for 9.23% of the total number, and 579 students with potential psychological distress, accounting for the total number 17.23% of the total number of people, 2 283 students without psychological distress, accounting for 67.99% of the total number. In the early, middle and late periods of the course, psychological problems showed a downward trend, and the main effect of time was significant(all P <0.01). After the implementation of the mental health course, the detection rate of serious psychological problems (3.84%, 129/3 358) was significantly lower than before the course(5.54%, 186/3 358)( χ 2= 10.82 , P <0.01). In the early, middle and late periods of the course, the development trajectory of freshmen s psychological problems was divided into two types, namely "first ascending and then descending" (26%) and "slowly descending"(74%). Conclusion The mental health curriculum shows a positive effect on improving the mental health of freshmen. Colleges and universities should pay attention to the construction of mental health curriculum to fully guarantee the quality of the curriculum.