Aiming at the problem of fixed Gaussian window function in the S transform, a Gaussian window adjustment factor is introduced to improve the algorithm, and a harmonic and interharmonic analysis method for photovoltaic power station based on generalized S transform is proposed. Firstly, the simulation model of the photovoltaic power station is built by MATLAB/Simulink, and the three-phase output voltage of the inverter is collected under natural sampling bipolar SPWM modulation mode. Then, taking the A phase voltage as an example, the generalized S transform is used to process the voltage signal to obtain a modular time-frequency matrix. Finally, the harmonic and interharmonic parameters of the photovoltaic power station are accurately calculated, which is achieved by analyzing the matrix. Simulation results show that the maximum amplitude calculation error of the method is only 3.30×10-4%, the average calculation error of frequency is 0%, which is much smaller than the S transform amplitude error of 35.19% and frequency error of 2.39%. The need for detection accuracy of harmonics and interharmonics can be met in photovoltaic power station.