Based on the theory of social exchange, this paper explores the effect and mechanism of corporate social responsibility on organizational citizenship behavior of employees, and tests the hypothesis with empirical data. The results show that the perceived internal and external corporate social responsibilities of employees have a positive impact on organizational citizenship behavior, in which the impact of external social responsibility perception is greater than that of internal social responsibility perception; organizational trust completely mediates the impact of internal social responsibility perception on organizational citizenship behavior, and some mediates the impact of external responsibility perception on organizational citizenship behavior.