The study of irradiation defects of HgCdTe photovoltaic detectors by 60Co γ has been carried out.The current-voltage measurement method was used to evaluate the irradiation effects.It was obtained that the dark current of detectors at a larger reverse bias has a more obvious correlation with the density of defect centers using the numerical differentiate method.By studying the variation of dark current with the extension of time,it was thought that the transient and permanent irradiation defects existed in HgCdTe photodetectors after γ irradiation.This phenomenon may be applied to infrared detectors which operate in the irradiation condition to lengthen the lifetime of infrared detectors.