Abstract: Due to the capacitive effect of power cables,the phenomenon of harmonic resonance amplification tends to occur in the offshore wind power collection system via power cables,which leads to decline in power quality.The distributed power flow controller（DPFC） is a device based on the voltage source converter,which can regulate power flow and control harmonics at the same time.In this paper,the frequency-domain correlation model of the offshore wind power system is constructed,and the reason for harmonic resonance amplification is analyzed based on this model.Then,the harmonic mitigation method of connecting the DPFC to the offshore wind power system is proposed,and the harmonic characteristics of the offshore wind power system with the DPFC are derived.Based on the these characteristics,a control strategy is designed,which reduces the harmonic voltage content of the grid-connected point by controlling the DPFC to track the harmonic compensation voltage that makes the harmonic voltage amplitude at the grid-connected point zero in real time.The simulation results show that the proposed harmonic mitigation method and control strategy of the offshore wind power system based on DPFC can effectively reduce the harmonic voltage at the gridconnected point and improve the power quality.