When the signal contains frequency components which are close to each other, traditional empirical mode decomposition (EMD) method was prone to the mode mixing phenomenon, leading to decomposed intrinsic mode functions lost their physical meaning. For this phenomenon, a new processing method is introduced. The differential operator which was combined with EMD decomposition can effectively suppress the modal aliasing. Simulation and practical engineering applications show that this method is superior to the traditional EMD algorithm. It can not only effectively separate frequencies that have close intrinsic mode functions, but also expand the scope of application of the EMD method.