Abstract: For the analysis of the trailing phenomenon of the partial discharge signal acquired by UHF antenna, the Influence of the UHF signal tailing are analyzed based on the transfer function of the UHF antenna——the amplitude flatness of transfer function and the group delay flatness. The calculation method of the two flatness parameters are proposed based on the existing UHF antenna effective height calibration system. The time domain impulse response of six UHF antennas are acquired by the measurement platform consisted by a GTEM cell and a pulse signal generator, and the two flatness parameters are extracted respectively. The maximum correlation coefficient and the oscillating coefficient are extracted which are used to described the tailing phenomenon, and the correlation of the two flatness parameters and them are calculated. The results show that the correlation of the amplitude flatness of transfer function and tailing phenomenon is greater than 0.57，and the correlation of the grope delay flatness and tailing phenomenon is greater than 0.87. The UHF signals are acquired in the same simulated partial discharge source, the correlation of the amplitude flatness and tailing time is 0.58, and the correlation of the grope delay flatness and tailing time is 0.91. The experimental results prove the effectiveness of the two parameters, and provide the basis for UHF antenna design and type selection.