The rights of employees are usually protected through the union when they perceive the company has breached their psychological contracts. This study, based on a sample of 199 employees from 16 enterprises and using the union president appointment as a moderator, looks into the relations between perceived psychological contract breach and employees' participation in the union activities. The result of the study demonstrates that the perceived psychological contract breach has a significant negative impact on employees' activities participation, whilst the union president appointment plays a regulatory role between the perceived psychological contract breach and the employees' participation in the union activities. Hence, the direct election of union president can guarantee employees' rights protection through the union, providing guidance on building harmonious labor management relations.