While an employees' job engagement directly or indirectly effects an organization's value creation, competitiveness, and development prospects, to explore the impact of employees’ psychological contract breakdown on their job engagement thus, has important theoretical and practical significance. This study, by integrating social exchange theory with resource preservation theory, explores the mechanism and boundary conditions of the impact of psychological contract breakdown on the employees’ job engagement. The empirical test results indicate that the breakdown of the employees' psychological contract has a negative effect on their job engagement, and has a significant positive impact on their work insecurity, whilst work insecurity plays a completely intermediary role in the impact of psychological contract breakdown on the employees’ job engagement. To reduce the employee's psychological contracts breakdown, this study suggests that organizations should play a positive role in communicating with employees, and assist employees in their career planning by providing them with necessary training opportunities and career development channels. Moreover, managers should assist employees in establishing and developing long-term, reciprocal and interdependent high- quality exchange relationships with their organizations and colleagues.