To study the nonlinear behavior of multi-module inverter parallel system under peak current mode，the topology module under synchronous control is analyzed. Through theoretical analysis, and simulation comparison, the parallel system is equivalent to the single-moudle H-bridge inverter. This system is a time-varying parameter system and we found in the research that it is easy to produce fast-scale instability in time domain, and slope compensation is a simple and effective method. Based on the nonlinear theory of equivalent single-moudle H-bridge inverter, the theoretical requirements of slope compensation signal amplitude of multi-module H-bridge inverter parallel system are analyzed and calculated, and the simulation verification and numerical analysis are carried out.