Abstract: In order to meet the requirements of wide frequency band, miniaturization and high gain for ultra high frequency sensors used to detect partial discharge in gas insulated substation(GIS), a multi frequency broadband composite hollow antenna embedded in epoxy resin is designed. The overall size of the antenna is 65 mm×65 mm×18.5 mm, with a simple structure and small volume. The antenna radiation layer and grounding layer are both cut from pure copper sheets with a thickness of 0.3 mm, and packaged to maintain structural strength. At the same time, bending and folding technology is used to reduce the antenna size, and multiple radiation units are composite loaded to broaden the detection frequency band. The experimental test shows that the voltage standing wave ratio(VSWR) of the multi frequency point broadband composite hollow antenna embedded in the epoxy resin is less than 5 in the 700 MHz-3 GHz frequency band, less than 2 in the 1.25-1.42 GHz, 1.48-1.93 GHz, 2-2.12 GHz and 2.66-2.75 GHz frequency band, and the maximum gain is 6.7 dB. It can effectively receive weak ultra high frequency signals and can be used for on-site detection of GIS partial discharge.