In recent years, the harmonic pollution is an important factor to impact on safe and stable operation of the power system. This paper summarizes the harmonic detection methods based on the study. First, In order to clarify the main harmonic components of power system, harmonic generation mechanism of the rectifier load and impact load is briefly analyzed. Then, the harmonic detection methods of FFT and wavelet transform which are the most commonly used have been introduced. Finally, the harmonic model and the measured data of the substation have been analyzed by Matlab simulation software, and compared the strengths and weaknesses of two methods. Analysis shows that the Fourier analysis have the ability to accurately reflect the signal amplitude and phase characteristics in the frequency domain, and the wavelet transform can visually display the waveform information of fundamental and harmonics in the time domain and frequency domain. In practical engineering applications, in order to get fast and accurate results, it is necessary to select the appropriate algorithm, which combined with the advantages of various harmonic detection methods.