Abstract: The interharmonic problem is a new focus in the research field of power quality. It is not an integer multiple of fundamental and usually with small amplitude. In terms of these identities, a new method of interharmoic detection based on iterative spectrum estimation method with variable frequency resolution combined with support vector machine (SVM) is presented in this paper. Compared with transitional FFT, higher frequency resolution can be obtained by the proposed approach during the same sampling time. Moreover the iterative method has no problems with spectral leakage, so the frequencies detected don’t need to be modified in the asynchronous sampling case. Combined with the above method, amplitudes and phases of interharmonics can be estimated with SVM method in a shorter calculating time after frequency precalculating accurately. The simulation with Matlab validates the approach proposed.