The invention discloses a method of suppressing the resonance of a photovoltaic grid-connected system based on improved deadbeat, including the following steps: analyzing the cause of resonance; constructing an improved deadbeat control strategy according to the result of analysis, wherein the improved deadbeat control strategy is to predict the sampling current at a time k+2, calculate the PWM duty ratio Dk+1 of an inverter at a time k+1, and implement the PWM duty ratio Dk+1 in the photovoltaic grid-connected system at the time k+1; and combining the improved deadbeat control strategy with a virtual harmonic impedance method to suppress the resonance of the photovoltaic grid-connected system. The method can be used to suppress the resonance of the system.