Severe electromagnetic interference (EMI) problem is blocking the development of power converters nowadays. To attenuate the side effect of EMI noise, passive filters are commonly used in various power converters. Nevertheless, passive filters have the shortcomings of large volume and heavy weight. To overcome these, active EMI filter (AEF) is under widely research and some results are published, which make it has the tendency to replace passive filters gradually. In this paper, a novel CM active EMI filter based on isolated voltage sensing approach is proposed. Compared with traditional voltage sensing network and current sensing network, the proposed sensing approach combines the merits of them, which means it’s isolated from the main circuit and has less impact on the impedance of original CM inductor. The effectiveness of the CM AEF is verified by the theoretical analysis, simulation and experiments.