Harmonic resonance endangers seriously safe and reliable operation of grid and an appropriate resonance harmonic analysis method is of great importance. The traditional mode analysis method is a kind of main method to analyze harmonic resonance of grid so to obtain various harmonic information such as resonance frequency

maximum excitation node and observation node as well as participation factor. However

its calculation efficiency is lower and has no way to judge accurately the maximum excitation node in the harmonic resonance of the distribution grid. The improved mode analysis method proposed in this paper combines the frequency spectrum analysis with the traditional mode analysis method

and the condition whether the judgment excitation node can occur resonance at resonance frequency is added. It is shown by the simulation result that the method proposed in this paper can effectively and accurately determine harmonic resonance frequency and maximum excitation node of distribution grid.