A distributed temperature sensor based on fiber grating of cable is presented in this paper.It can monitor temperature of cable real-time.Based on equation of heat conduction,finite-element method is used to analyze temperature field of cable and provides witness for monitor temperature.The fiber grating is not electrification,has good ability of anti-jamming and radioresistance,it is suit to as the temperature sensor in high-tension electricity environment.In 20～100 ℃,the central wavelength of FBG vary with the temperature has fine linearity.The standard thermojunction temperature sensor and fiber grating temperature sensor are used to do contrast experiment.The experiment result indicates that the curve of time-temperature has good follow character and temperature difference less than 1 ℃.So it can accurately measure temperature of cable.