In this paper, a fault detection method for distribution lines based on CDMA spread spectrum technology is proposed to solve the problems of insufficient sensitivity and limited anti-interference ability in traditional fault detection methods for distribution lines. The technique uses CDMA spread spectrum technology to evenly disperse the injected signal energy into the whole frequency band, reduces the influence of the narrowband interference on the distribution line, and improves the ability of long-distance fault location of the distribution line. The system is divided into two parts: high-frequency signal injection and high-frequency coupling signal reception. The fault propagation time is calculated by making full use of the correlation between the received signal and the transmitted signal to judge the fault location. This paper discusses the generation and injection of the CDMA spread spectrum signal, the reception of the coupling signal, the modulation and demodulation of the CDMA signal, and the system simulation and experimental verification of the fault location algorithm in detail. The system simulation and experimental results illustrate that the proposed method has high fault detection accuracy and reliability in complex distribution networks.