When using the spread spectrum time domain reflectometry for cable fault detection, it is difficult to effectively identify near-distance faults due to the presence of detection blind spot. This not only reduces the detection range but also limits its wide applicability in practical applications. In response to this issue, this paper thoroughly analyzes the mechanism behind the formation of blind spot, and proposes a signal separation-based method to eliminate them. Leveraging the linear superposition of incident and reflected signals, this method applies subtraction in digital signal processing to successfully separate the two signals, enabling accurate identification of reflected signals within the blind zone and extraction of fault information. This method eliminates blind spot through digital signal processing technology, avoiding changes to the hardware platform. The algorithm is simple, easy to implement, and adaptable to a wide range of scenarios. Experimental results show that using this method for online detection of open and short circuit faults in a detection system with a central frequency of 62.5 MHz, the maximum absolute error is only 0.16 m, fully demonstrating its effectiveness and practicality.