In order to discuss the future of applying Distributed Optical Fiber Grating Technology in HV cable insulation online monitoring,firstly the paper illuminates the principle and characteristic of this technology.We have optimized the sensor design,and tests have been carried out on a 220 kV HV cable for a year.During the temperature testing,measurement accuracy,response performance and stability of the apparatus are tested.The result proves that measurement error range varies within 0.5 ℃,response time is within 6 s and it can measure the temperature in long distance and large area.This technology can be very effective in online monitoring cable temperature,and it can provide direct data for calculating cable current rating and keep the cable away from fire.This paper discusses the probability to apply this technology in cable insulation online monitoring.The test result shows it can provide a new way to realize cable insulation online monitoring.