We designed a sensor of Moore fractal antenna for detecting partial discharge (PD) in gas insulated substations (GISs), which is working at ultra-high frequency, and analyzed the multi-frequency characteristics of this antenna. According to the simulation results, we made a Moore fractal antenna. The Moore fractal antenna is small and its structure is simple. Besides, the antenna has an ultra-wide-band frequency, as well as great directivity and omnidirectional radiation feature. The partial discharge was tested in the laboratory, detected by Moore fractal antenna and external UHF sensor. Compared the measurement results, the proposed antenna is quite promising for PD on-line detection applications.