A central 60° synchronous modulation method was presented for neutral point clamped three-level inverter used in themulti-mode PWM modulation strategy, which could calculate switching angle in real time. Principle of the modulation method with differentcarrier frequency ratios was introduced, and relationship between switching angle and modulation wave was derived, as well as switchingstrategy. According to this method, a simulation model of drive system with three-level inverter and induction motor was built, andasynchronous modulation, 5 frequency division synchronous modulation 3 frequency division synchronous modulation and square wave areawere simulated. The simulation showed that with the method, output voltage values met the requirements of good symmetry even in case oflow carrier frequency ratio, and smooth switching among different modulation could also be accomplished.