Abstract: In modern warfare, various anti-radiation weapons pose a serious threat to the survivability of active positioning systems. Electronic support measurement (ESM) system, which are based on multi-point time difference of arrival (TDOA) positioning, can passively receive and track electromagnetic signals emitted by targets, serving as an important passive detection method. However, during actual operations, when the ESM system uses communication signals for TDOA positioning of targets, the presence of communication interference signals leads to a certain degree of decline in the ESM system's ability to track and locate communication signals. In this paper, we analyze the characteristics of communication signals and communication interference signals and propose a multi-frequency interference suppression method based on cascaded digital filters. We also introduce its basic principles and engineering implementation methods. Simulation experiments have verified that this method can effectively suppress communication interference and enhance the ESM system's detection capability for communication signals under interference conditions, demonstrating significant engineering value.