The present invention provides a control method capable of improving the system dynamic response of a grid-connected inverter under weak power grid transient state operation. According to the method, two modes are involved. Under the mode 1, namely, a steady state working mode, the proportionality coefficient Kp and integral coefficient Kp of the control parameters of a phase-locked loop are set to be the parameters of the steady state working mode respectively, namely a proportionality coefficient Kp1 and an integral coefficient Ki1, and therefore, the stability of the inverter system under a weak power grid condition can be improved. Under the mode 2, namely, a transient state working mode, the proportionality coefficient Kp and integral coefficient Ki of the control parameters of the phase-locked loop are set to be the parameters of the transient state working mode respectively, namely a proportionality coefficient Kp2 and an integral coefficient Ki2, and therefore, the dynamic characteristic of the inverter system can be improved. With the control method of the invention adopted, the defects of small bandwidth of the phase-locked loop and the poor control dynamic property of the grid-connected inverter when the grid-connected inverter operates under the weak power grid transient state can be eliminated.