This paper analysis the work principle of peak current mode H bridge converter. It can observe the system exhibits a kind of special nonlinear phenomenon: breathing phenomenon. When the disturbance signal frequency is not different with the switching frequency and there is a certain degree of disturbance signal intensity, it will produce breathing phenomenon through the modeling and numerical simulation to the system. We can know the theoretical analysis is same with the numerical simulation. At last, it discusses the change of circuit parameters Iref, E, L / T to impact degree of disturbance signal intensity to generate breathing. It can provide theoretical basis for stability design of H bridge converter.