The invention provides an impedance identification method of a power grid of a grid-connected inverter based on high-frequency signal injection. The method comprises the following steps: firstly, respectively measuring the voltage and bridge arm side current of the grid-connected inverter by using a voltage sensor and a current sensor, and converting the voltage and the bridge arm side current through a proportional integral controller to obtain a modulated voltage signal; then, injecting a three-phase high-frequency voltage signal into the modulated voltage signal to update the voltage of thegrid-connected inverter, measuring the power grid side current of the grid-connected inverter by using the current sensor, and respectively substituting the updated voltage and the power grid side current into a voltage extraction module and a current extraction module; and finally, extracting a high-frequency voltage signal and a high-frequency current signal of a grid of the grid-connected inverter by using an improved complex number filter so as to solve an impedance value of the power grid in real time. According to the impedance identification method provided by the invention, the three-phase high-frequency voltage signal is directly superimposed on the modulated voltage signal, thereby ensuring the effective injection of the high-frequency signal and being able to improve the signal-to-noise ratio of the power grid, so that the impedance identification accuracy of the power grid is improved.