Aiming at the heat problem for cubicletype substations, based on FBG sensing technology, an online realtime temperature monitoring system is designed, and it realized the remote temperature monitoring at 11 positions inside cubicletype substation including the transformer, transmission cable connector and box shell. The temperature data all daylong well reflected the temperature variation of the monitored points; what is more, the results can be used for the development of early warning system for facilities protection. Compared with the traditional measurement methods, it has the advantages of insulation, high voltage resistance and antielectromagnetic interference, and it can be applied on temperature monitoring in different electrical environment.