In response to the problem of high-frequency composite noise in ±800kV Converter Station built-in ultra-high frequency partial discharge detection, which interferes and masks partial discharge signals, and cannot obtain accurate partial discharge waveforms, this paper focuses on the wideband extended circuit model and proposes a wideband extended circuit noise control method based on fractional order filtering system. The effectiveness, stability, and reliability of this method in controlling high-frequency composite noise in UHF partial discharge detection were verified and calculated through two parameters, namely ”root mean square value (RMS)” and ”waveform range (R)”. Laboratory experiments, on-site environmental tests, and finite element Maxwell 3D electrostatic field module simulation calculations were conducted to verify the effectiveness, stability, and reliability of this method.