Abstract: The transient synchronization stability mechanism of the grid-forming converter and the grid-following converter is studied, and the simulation verification is completed based on the actual power grid scenario. Firstly, according to the control strategy of the nonsynchronous-machine sources, the key factors influencing its transient synchronization stability are analyzed. Then, the time domain simulation model of 500 kV equivalent AC system of Zhejiang Jinhua is built in PSCAD/EMTDC. Based on this model, the transient instability characteristics after short-circuit faults of the actual power gird with nonsynchronous-machine sources are studied, and the key factors influencing the transient stability are verified by simulation.