Abstract: In view of problem of unbalanced output power of each H-bridge for staircase modulation of cascaded multilevel inverter, a power balance control strategy for staircase modulation of adjusting pulse switching angle was proposed, which realized power balance in one output cycle through interchanging output voltage of the H-bridge each 1/4 output cycle. Meanwhile, an improved particle swarm optimization algorithm based on dynamic change of inertia weight was applied into solution of switching angles of power balance control strategy for staircase modulation, which could get the optimal solution of switching angle quickly and efficiently by dynamically decreasing inertia weight with increase of evolution algebra without initial value. The simulation results verify feasibility and validity of power balance control strategy for staircase modulation based on improved particle swarm optimization algorithm.