Due to constant switching frequency, the switching loss of the flyback single-phase photovoltaic grid-connected micro-inverter working at discontinuous conduction mode is large when the sinusoidal wave is near zero or the instantaneous output power is low．So, a novel DCM variable frequency control strategy is proposed in this paper. With this control strategy, the switching frequency varies with the instantaneous output power, and the switching frequency can be reduced independently at the low instantaneous output power, which can effectively reduce the switching loss. The proposed control strategy is implemented by constant primary current peak unit and switching frequency control unit. Finally, the feasibility of the flyback single-phase photovoltaic grid-connected inverter with DCM variable frequency control is verified by PSIM simulation software. The simulation results show that the proposed control strategy can effectively reduce the switching frequency when the sinusoidal wave is near zero or the instantaneous output power is low, thus reducing the switching loss and improving the overall efficiency of the inverter. It also ensures that the output current has a smaller THD.