Abstract: To solve the problems of poor operation reliability and high fault probability of underground high-voltage cable joint,the paper proposed a design scheme of on-line monitoring system of temperature of high-voltage cable joint of mine, gave overall structure of the system,introduced design of hardware and software of the system in details.The experiment result showed that the system has advantages of stable running and high reliability and its each index meets with national standards for coal industry and actual operation requirements,which has a practical value.