The discharging process of polyvinyl pyrrolidone electret under two different heating rates 3.5 and 2 A degrees C/min has been investigated by the measurement of thermally stimulated depolarization current (TSDC) in the temperature range from 30 to 250 A degrees C. The TSDC spectra of PVP shows three peaks located at 70 +/- A 10, 150 +/- A 10, and 230 +/- A 10 A degrees C, respectively. When explaining the TSDC spectra, this thesis deduced that the first peak, beta peak, originates from side group relaxation; the second peak, alpha peak, corresponds to the relaxation of the frozen dipoles on the molecule chain segments during glass transition; the third peak, rho peak, is attributed to the detrapping of the trapped space charge under thermal stimulation. The current of the rho peak is remarkably strong due to the fact that PVP molecules' side groups-the pyrrolidone rings containing lactam structure-are strong polar groups which cause the great increase in the number of bulk traps, trapped space charge, as well as detrapped space charge under thermal stimulation.