Accurate harmonics and inter-harmonics measurement in the electrical power system is the precondition and foundation of harmonic mitigation.Bearing in mind the development status of harmonic detection technologies worldwide，starting with detection signal model，various methods and their characteristics for the harmonic analysis with different signal models，such as discrete Fourier transform（DFT），spectrum estimation and Hilbert-Huang transform（HHT）are discussed in details，and some research points in the future are proposed.