Kinetics of electron-detrapping process of Ir dopants in AgCl emulsion grains was studied by photo-induced ESR measurement. We made the kinetic model to analyze the lifetime of electrons trapped by Ir dopants quantitatively. The ESR signal was attenuated in a double-exponential way. The fast decay indicated the electron-detrapping process of Ir dopants, and the slow decay corresponded to the “desensitizaton” in photographic process.