Abstract: There are three different modes in the discharge process which include corona discharge, partial discharge and arcing and their characteristics are different. A close relationship is shown between the contamination discharge intensity and characteristics of acoustic emission signals by a large number of tests and studies. Contaminated insulator discharge test was carried out, and a lot of experimental data about acoustic emission signal on contamination discharge was obtained. Based on the experimental data, the extraction method of the characteristics of acoustic emission signals is researched which included energy, the amplitude and frequency. Based on the energy, the amplitude and frequency, the final contamination discharge mode is identified.