Abstract: The existing DC crosstalk fault detection methods have problems such as complex processes, difficult implementation, and insulation hazards. Therefore, this paper proposes a DC crosstalk fault detection and localization method based on variable bridge. This method utilizes a variable bridge of a system to inject low-frequency AC signals into the bus through periodic switching of ground resistance. By detecting the presence of the same frequency component in the bus voltage of another system, it determines the crosstalk fault. The strategy of alternating injection and detection between two systems is adopted to accurately locate the crosstalk branch. Based on the dual-frequency method, quantitative measurement of the crosstalk resistance is achieved. The effectiveness of this method is verified through simulation experiments.