Abstract::Aiming at solving the problem of harmonic detection, several traditional methods of analysis have been proposed.It was the first time that the harmonic detection method based on Variational Mode Decomposition(VMD) was proposed. Electrical signals were decomposed into a series of intrinsic mode function (IMF) by using the VMD method and then the instantaneous frequency and instantaneous amplitude value of each IMF were gained after the transforming of IMF decomposed through Hilbert-Huang transforming(HHT).For the VMD method decomposed each IMF accurately, the instantaneous frequency and amplitude value could be obtained accurately. And after the comparison of the results of IMF gained based on Empirical Mode Decomposition (EMD) with the results of IMF gained based on Hilbert-Huang transforming, it was proved that VMD method showed stronger decomposition ability than traditional Hilbert transforming. In order to test the function of VMD on algorithm, VMD calculation and the traditional instantaneous harmonic detection were applied to practical data. Results on simulation and experimental statistics showed that the method could be regarded as an effective method to detect harmonics.