Abstract: In the sinusoidal pulse width modulation (SPWM) inverters, the output voltage contains lots ofhigh frequency harmonics. These harmonics may bring about serious electromagnetic interface problem and reducethe reliability of the system. According to output harmonic analysis of the conventional SPWM inverter, this paperproposes a harmonic suppression method adopted random frequency modulation in the SPWM inverter. Thismethod can make the harmonic spectrum of inverter output voltage be continuously distributes without affectingthe fundamental frequency component, and thus the harmonic energy of inverter output can distribute more equably.By adopted this method, the peak value of output voltage harmonic spectrum decreased and electromagneticinterface reduced. Based on the theoretical analysis and simulation, a 1 kW experimental prototype is designed.Comparative test shows that the peak value of harmonic in the SPWM inverter adopted our proposed method isreduced about 10dB than the conventional one.