The invention discloses a power signal harmonic analysis method which comprises the steps of (1) selecting a phase voltage or a phase current, utilizing a high-frequency counting clock for counting power frequency signals, obtaining a total counting value through a plurality of periods, dividing the total counting value by the number of the periods to obtain the average counting value of the power frequency signals, (2) determining the counting step length of the sampling periods as time intervals of the sampling periods, (3) obtaining an initial point of the power frequency signals through circuit detection, (4) conducting the Fourier conversion in the DFT mode, and only calculating the amplitude and the phase angle of an interested harmonic component.