Er3＋ and Li＋ codoped Y3Al5O12（YAG） powders were prepared for a systematic investigation of their upconversion emissions.X-ray diffraction（XRD）,upconversion emission spectra,pump power dependence,FT-IR spectra and decay time were studied to characterize the samples.With Li＋ doping,the upconversion emission intensity of Er3＋ doped YAG powders was obviously enhanced,accompanied with an increase in the ratio of green to red intensity.The enhancement of emission intensity could be attributed to two mechanisms：one was the distortion of local crystal field around Er3＋,and the other was the decrease in the amount of CO32-and OH-groups.Our results revealed that the latter was the dominant mechanism of the upconversion intensity enhancement in the YAG：Er3＋/Li＋ powders.
