For the issue of low utilization rate of DC voltage on the traditional voltage source multilevel inverter, the idea of third harmonic injection is introduced to the carrier phase shifting technique based on the mathematical analysis of carrier phase shifting SPWM modulation technique, and the carrier phase shifting THI-PWM modulation technique which is applicable to multilevel inverter is proposed, making the form factor of the system rose from 1.732 to 2 and the utilization rate of DC voltage increase about 15%. A three-phase five-level inverter simulation model is built in Matlab/Simulink, the simulation result demonstrates the correctness and the validity of the theory.