The impedance measurement method based on harmonic injection has the advantage of harmonic control, and it has been widely used in impedance measurement. In this paper, a method for measuring harmonic impedance of medium and low voltage distribution network based on inverter power supply is introduced, and different test topologies are designed for distribution networks with different voltage levels. The principle of measuring harmonic impedance of low voltage distribution network by harmonic voltage is analyzed, at the same time, the Thevenin model of inverter power supply with different control methods is established, and the characteristics of the equivalent circuit under different control are analyzed. To improve the measurement accuracy and meet the grid harmonic requirements during the test, a criterion of harmonic injection is proposed. Finally, the simulation proves that the harmonic impedance measurement method based on the inverter power supply can accurately measure the impedance parameters of the distribution network.