As an important role in electromagnetic interference (EMI) solving of switching power supply, the EMI filter's performance and integrated design are of great significance to improve the power density of switching power supply. This paper combines the basic means of magnetic integration and electrical integration of the filter and utilizes the integration advantages of flexible multilayer foils (FMLFs) to integrate the common and differential mode inductor and Y capacitor of the filter into a unit module. At the same time, the design value of the differential mode inductor is increased through the decoupling design of the common and differential mode inductor. Compared with the traditional discrete filter, the integrated filter omits the Y capacitance and reduces the X capacitance, which can effectively reduce the board area of the EMI filter on the premise of consistent performance. Combined with the design process of the integrated filter, to improve the integration, this paper mainly discusses the process of core selection, performance prediction, and performance modeling, and finally verifies the feasibility and effectiveness of this scheme through a noise comparison experiment.