The on-line temperature monitoring for power cable joints can effectively prevent and reduce the accidents of cable joints. This article introduces a new type of temperature monitor and analysis system for urban power cable joints, based on GPRS data transmission. The platform has the functions of alarm and joint state assessment analysis. Power supply device was designed and developed based on supercapacitor, that is obtained power directly from the power line by tailor-made current transformer, it can solve the difficult point effectively.