Abstract: The complexity of the control strategy of the virtual synchronous generator（VSG） makes it present rich transient characteristics. Clarifying the fault characteristics of VSG is of great significance for the adaptability analysis and the new principle study of grid-forming protection. Existing studies on VSG fault characteristics mainly focus on symmetric short circuit and constant internal potential, but do not involve asymmetric short-circuit scenarios and do not take into account the effect of internal potential change on the analytical calculation of the short-circuit current. To address the above problems, this paper proposes a transient current analytic calculation method for the VSG with asymmetric short circuit considering the influence of the internal potential change. Firstly, based on the balancing current and fault current limiting control strategy during the asymmetric short circuit, the characteristics of the internal potential of VSG under the influence of different reactive power reference values are analyzed.Secondly, the equation between the short-circuit current and the internal potential is established based on the virtual impedance loop so as to clarify the influence of the internal potential change on the transient characteristics of the short-circuit current. Then,the differential equations between the short-circuit current and the internal potential are established based on the analysis of the dynamic characteristics of the reactive power-voltage loop. Thirdly, the analytical expressions of the internal potential and the shortcircuit current can be obtained by associating the above equations. Finally, the correctness of the derived analytical formula is verified by digital simulation and real-time simulation.