Abstract:This paper presents a multicore cable test device based on the time domain reflectometry(TDR). A microcontroller of C8051F005 is used for controling CPLD to send pulse signal to the cable. With this design and dual joint measurement mode, the faults of cable shorted, mixed and the position of borken wires can be quickly detected and the presion of fault fixedpoint position can be within 5 m. Because of the low cost and convenient operation,the design will have good application prospects.