Abstract: In a hybrid power system where renewable energy generation units and synchronous generators are jointly connected, the interaction between renewable energy with different synchronization modes, and between renewable energy and synchronous generators are all complex, deeply affecting the transient synchronization stability of the hybrid system. To reveal the dynamic coupling mechanism among different generation units under symmetrical grid fault and its impact on the transient synchronization stability of the system, this paper firstly establishes a mathematical model for transient stability analysis of a hybrid systems. Subsequently, the space vector graphical method and phase portrait method are used to analyze the impact of injection current and phase-locked loop parameters of grid following renewable energy generation units, power control loop parameters of grid forming renewable energy generation units on the transient synchronization stability of the hybrid system in detail. Based on this, the design principles of system controller parameters are given. Finally, the correctness of the theoretical analysis is verified through simulations under different operating conditions.