The invention relates to a processing method during synchronous pulse width modulation carrier to noise ratio switching of an inverter. A transition time slot is added between a switching frequency fs1 under the former carrier to noise ratio and a switching frequency fs2 under a new carrier to noise ratio during synchronous pulse width modulation switching of different carrier to noise ratios; and a transition frequency fst which is higher than the switching frequencies fs1 and fs2 before and after being subjected to switching is set in a transition time slot so that the switching frequency fs1 is improved to the transition frequency fst and continues for a center time and reaches a steady state and then the transition frequency fst is switched to the switching frequency fs2 with lower frequency. During the carrier to noise ratio switching of the synchronous pulse width modulation, the transient state impulse current during the swinging of the switching frequency from the fs1 to the fst and the swinging of the switching frequency from the fst to the fs2 is less than the transient state impulse current during the switching of the switching frequency from the fs1 to the fs2 directlyin the traditional method.