Abstract: Carrier injection under liquid nitrogen temperature followed by thermal stimulated current(TSC) measurements were carried out for MPCVD diamond films. TSC peaks were observed obviously for as-grown samples.The peaks,however,almost disappeared after the first heating process.Having undergone hydrogen plasma treatment at ~900℃ for 2.5 hours for one sample,the peaks emerge again. Thermal stimulated traps emptying is postulated to be the origin of the TSC peaks, and the traps are related to hydrogen implantation.These traps,which energy level located in the band gap of diamond, can be eliminated via proper heat treatment.