In order to solve the problems of existing multi-core cable fault diagnosis system, such as difficulty in operation and low efficiency, design cable fault analysis and quick diagnosis system. The fault tree analysis was used to qualitatively analyze the multi-core cable, and then combined with FMECA to evaluate and predict fault tree bottom events. According to the fault analysis results, a fast fault diagnosis system of cable fault was designed in this paper. The hardware control platform in the system adopts STM32 + CPLD architecture, used visual C++ to compile the human-computer interaction interface, and design with the thought of control modular. Verify the technology with the test. The test results show that the system can quickly and correctly detect cable, and it has a stable and reliable work, easy operation, high efficiency.