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 is based on multi-point time difference of arrival (TDOA) positioning, can passively receive and track electromagnetic signals emitted by targets. It has many advantages such as resistance to anti-radiation weapon attacks, anti-jamming, anti-detection, and anti-stealth, and is an important passive detection method. However, during actual operations, when the ESM system uses communication signals for positioning targets based on TDOA, 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, the characteristics of communication signals and communication interference signals are analyzed and a multi-frequency interference suppression method based on cascaded digital filters is proposed. Also, its basic principles and the method for its implementation in engineering are introduced. 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 high value in engineering applications.