Abstract: The research group designed a multi-overlapping plus-inverters device based on circular transformer, and applied the principle of rotating magnetic field to eliminate harmonics. In order to solve the problems of low switching frequency and large volume and weight of this inverter, a harmonic injection inverter based on circular transformer is proposed by using the idea of harmonic injection in active filter principle for reference. The device consists of auxiliary inverters and main parts. The main part is a main inverter and a circular transformer. The auxiliary inverters consist of two groups of three-phase inverters. The principle of phase shift superposition is used to generate a specific harmonic magnetomotive force. In the circular transformer, the principle of rotating magnetic field is applied to inject the output of the main inverters voltage to eliminate harmonics. The structure characteristics and working principle of the inverters are described. The effectiveness of the inverters is verified by simulation.