Aiming at the shortage of submarine cable operation and maintenance technology, especially online fault location methods, such as GPS time synchronization online location system circuit’s complexity, high cost, poor reliability and low location accuracy, this paper proposes a submarine cable fault location system and method based on optical fiber pulse transmission. The system uses the optical fiber in the submarine cable to transmit the pulse signal. By optimizing and designing the programmable counting unit to delay the square wave pulse and the location algorithm, the test blind zone is eliminated, and the online fault location detection function of the submarine cable is realized. The test results show that the system has the advantages of simple hardware, high reliability, convenient installation and high location accuracy. This technology has been applied for a national invention patent.