For the ultra-high frequency (UHF) PD detection system which is widely assembled by Power Grid Corp, it is always impossible to verify the validity. Based on the UHF signal spectrum of GIS typical defect type, the feature extraction and optimization of UHF spectrum signals under different defect types are carried out respectively. And according to this characteristic, the UHF signal spectrum is optimized in 0-50V range. A true GIS PD signal source is designed to simulate the UHF signals of various typical insulation faults and tested, the test result is good, and it shows a good application prospect in the checkout of the UHF detection system in GIS.