Currently, the detection of foreign objects in wireless charging of electric vehicles is usually carried out using auxiliary detection coils. However, the signals collected from the auxiliary detection coils under strong power fields after starting wireless charging have significant interference, and it is difficult to effectively restrain interference using hardware filtering. In this paper, a method based on α-β digital filtering is proposed to filter the amplitude and phase signals of foreign object detection under strong power magnetic field, so as to reduce signal interference and improve the reliability of foreign object detection. In this paper, an α-β digital filtering algorithm is designed and simulated, and compared with some common digital filtering algorithms, the results show that the α-β digital filtering algorithm is better.