Abstract: When the grid contains harmonic components,the DC side capacitor of the photovoltaic inverter will produce voltage ripple,which will not only affect the service life of the DC container,but also reduce the power quality of the system. According to the mechanism of DC voltage fluctuation of PV inverter and its characteristic of only outputting active power,this paper proposes a mirror virtual resistance technology to solve the problem of DC voltage fluctuation of PV inverter. This strategy only needs to add a small amount of calculation on the basis of the normal operation of the inverter,which can suppress the fluctuation of DC voltage and improve the power quality of PCC point,and has high practicability. For the harmonic component,the photovoltaic inverter is equivalent to a mirror virtual resistance with the same size and opposite direction as the fundamental equivalent resistance to absorb the harmonic power,and significantly reduce the DC side voltage fluctuation. The simulation and physical experiment results verify the effectiveness of the strategy.