Trichel pulse is a typical negative corona current with a high regular form, its detailed characteristics has not been discussed. Moreover, the differences in a train of Trichel pulses also have significant influence on the spectrum of the pulsatile corona current and thus the audible noise and radio interference. In this paper, a serious of experiment was conducted on a scale model of transmission line to investigate the detailed characteristic of the difference in a train of Trichel pulses. Based on the thorough analysis of the experimental data, the difference between the first pulse and the rest pulses of a train of Trichel pulses were amply described.