Abstract: Objective: The purpose of this study is to investigate the effect of social capital on the achievement motivation of elite college athletes and to examine the mediating role of self-esteem between the two. Methods: A total of 484 elite college athletes were surveyed using the Social Capital Questionnaire (SCQ), the Student Self Questionnaire (SSQ), and the Achievement Motives Scale (AMS). Structural Equation Modeling (SEM) with maximum likelihood estimation was used for data analysis, and the bootstrap (5000) method was employed to validate the mediating effects. Results: (1) No significant differences were found in gender, training duration and sports level in social capital (P>0.05); while significant differences were observed in education background and sports type (P<0.001). No significant differences were found in training duration and sports level in the motivation to pursue success and the motivation to avoid failure (P>0.05); while significant differences were observed in education background and sports type (P<0.001); Meanwhile, significant differences were found in gender in the motivation to pursue success (P<0.05). (2) Social capital positively predicted the motivation to pursue success (P<0.001); it also positively predicted the motivation to avoid failure (P<0.001); moreover, social capital positively predicted self-esteem (P<0.001), and self-esteem positively predicted the motivation to pursue success (P<0.001). (3) Self-esteem acted as a mediator between social capital and the motivation to pursue success (95%CI=0.106,0.428,95%CI=0.051,0.249). Conclusion: Among elite college athletes, social capital and achievement motivation do significantly differ in education background and sports type. Social capital positively predict achievement motivation, and self-esteem plays a mediating role between social capital and the motivation to achieve. The findings of this study have implications for understanding and enhancing the achievement motivation of elite college athletes.