Objective: This study explored the relationships among psychological stress, achievement motivation and psychological capital in college students to provide a reference for improving the level of psychological capital in college students. Methods: A multi stage stratified cluster sampling method was used to select 9 940 college students from ten universities in Anhui Province. The achievement motivation scale (AMS), psychological stress scale (SRQ-20) and psychological capital scale (PPQ) were applied. The moderating effect of the questionnaire was analyzed with χ 2 tests, Spearman rank correlation and stratified regression. Results: Statistical differences were found in psychological stress according to major, whether students leader, family economic status and whether students had left behind experience ( χ 2=15.50, 10.25, 28.61, 25.55, P <0.05). The rank correlation results indicated that psychological stress was negatively correlated with the pursuit of success ( r =-0.27) and four dimensions of self efficacy,optimism,hope and resilence in psychological capital ( r =-0.43, -0.41,-0.36,-0.45)( P <0.05), and was positively correlated with the avoidance of failure ( r =0.25, P <0.05). The stratified regression model indicated that psychological stress in the dimensions of college students achievement motivation (pursuit of success: β =0.02, Δ R 2=0.01, P <0.01; failure avoidance: β = 0.03 , Δ R 2=0.01, P <0.01) played a moderating role in the relationship between psychological capital and psychological capital. Conclusion Being female, senior students, low household economic status, and left behind experience are associated with more psychological stress among college students. Psychological stress is correlated with achievement motivation and psychological capital, and has a moderating effect on the relationship between achievement motivation and psychological capital.