Abstract: To meet the application requirements of the DC 270 V to DC 28 V power supply converter, a design procedure is proposed to suppress electromagnetic interference, caused by conduction and radiation at the input of the power converter. By analyzing the electromagnetic interference spectrum of the power supply converter, the filter parameters are calculated. To suppress filter oscillation, a method through arranging resistance-inductance network in parallel at both ends of the differential mode inductor is proposed, and it replaces the traditional method that adopted liquid aluminum capacitance and makes the reliability of the filter improved. Due to the DC component of current in the differential mode inductor is much higher than the AC component, the enameled flat copper wire is adopted to reel the winding to reduce the volume of differential mode inductance. Based on the characteristics that Mn-Zn ferrite has high magnetic conductivity at low frequency and Ni-Zn ferrite has stable magnetic conductivity at high frequency, the design of using common mode inductor with dual magnetic core is proposed, and it makes the common mode inductor achieve a wider frequency and a smaller volume. Finally, the experimental results verify that the power supply converter adopting the designed input EMI filter can meet the requirements of CE102 in GJB 151.