The constant-frequency synchronous current phasor control method for island microgrid has many advantages, such as the effect of power sharing between inverters, less affected by system parameters, strong resistance to voltage disturbance and simple implementation method. However, when it is applied to the microgrid with nonlinear unbalanced loads, there is the problem of voltage distortion and voltage unbalance. Therefore, a virtual harmonic resistance based constant-frequency synchronous current phasor control method was proposed. By introducing virtual harmonic resistors, the output impedance of the inverter in the low harmonic frequency domain was reduced, and the voltage distortion and voltage unbalance was suppressed. In the meantime, the harmonic current was evenly distributed among parallel inverters. The output impedance model of the inverter was established. According to the model analysis, it was found that the virtual harmonic resistance would cause resonance and amplify the high-order voltage harmonics. Therefore, active damping control is used to suppress resonance generation. The simulation and experimental results show that the proposed control method can effectively improve the voltage waveform quality and realize the reasonable averaging of harmonic current.