Abstract: During grid faults, the interaction between inverters and between inverters and the grid can easily lead to transient stability problems in the multi-inverter parallel system. In addition, most of the research objects of previous inverter transient stability analysis results and improvement strategies are single-inverter grid-connected systems, which may not be applicable to the multi-inverter parallel system. Aiming at this problem, we first established a transient synchronization model of the multi-inverter parallel system, and pointed out that multi-inverter interaction would change the equilibrium point existence and transient characteristic parameters. Then, under different grid fault initial states and inverter output characteristics, the influence of multi-inverter interaction on system transient stability was analyzed by using the equal-area criterion and the phase portrait. Based on this, a transient current injection strategy was proposed to realize the approximately constant equilibrium point before and after the grid fault to ensure the transient stable operation of each inverter and provide a reference for the setting of the transient current during the grid fault. Finally, simulation and experimental verification were conducted based on Matlab/Simulink simulation software and experimental platform. The results show that the proposed transient synchronization model can accurately reflect the system's transient response characteristics, and the proposed strategy can maximize the system's transient stability margin.