Abstract: To address the misjudgment in the transient stability analysis of virtual synchronous generators when only considering the swing equation, the impact of voltage dynamics at the points of common coupling on the transient behavior of the system is first considered. A transient model considering the dynamic characteristics of voltage is established to achieve a comprehensive and accurate depiction of the dynamic characteristics of the virtual synchronous generator. On this basis, a fast iterative algorithm for directly solving the critical clearing angle and the critical clearing time is proposed, and the mechanism that the changes in the core control parameters of the virtual synchronous generator may affect the transient stability of the system is analyzed. Finally, an electromagnetic transient model of a virtual synchronous generator with the typical structure is built to verify the correctness of the theoretical analysis and the proposed algorithm. The results show that, compared to the transient model that only considers the swing equation, the proposed model more accurately depicts the transient characteristics of the virtual synchronous generators.