In power production and operation process，the accurate length measurement and the mutation pointpositioning of parameters of the wire or cable are all of great significance for the construction of electricity，cablefault detection，high impedance ground fault diagnosis and production management of the cable． However，for thepulse reflection method of cable fault location，pulse source quality determines the accuracy of pulse reflection meth-od in cable fault location． This paper presents a design of pulse source for accurate positioning of cable faults，andgives the specific circuit design． The pulse width and voltage amplitude can be adjusted in the circuit，and the pulsesource was tested and used for accurate positioning of cable faults． Experimental results show that，pulse source isdesigned in this paper can produce a pulse width with 50 － 100 ns and pulse amplitude with 5 － 15 V，the test re-sults can be controlled within 5 meters of the blind area，meet the requirements of cable fault location，provide anew idea for low voltage nanosecond pulse source and a new method for the related technical field．