Based on Chinese cultural context, this paper explores the impact of organizational citizenship behavior on employee’s job performance and its internal mechanism. The empirical study suggests that organizational citizenship behavior has a significant positive impact on job performance and social capital plays a partial mediating role.Organizational citizenship behavior can improve the work performance of employees by increasing employees’social capital. In addition, the impression management has a significant positive impact between organizational citizenship behavior and social capital. Accordingly, it is recommended that corporate managers pay attention to the role of employees’organizational citizenship behavior in improving employee performance, and the managers attempt to exert the role of social capital in the transmission between organizational citizenship behavior and employee performance; enterprise employees should pay attention to the role of organizational citizenship behavior on their own social capital accumulation and work performance improvement, and combine with impression management behavior to fully enhance organizational citizenship behavior effectiveness.