Electron trapping material ZnS:Cu,Pb,Mn were analyzed by XRD, and the optical properties were measured. The measurement included fluorescence spectrum, fluorescence excitation spectrum, infrared stimulated luminescence spectrum, infrared stimulation spectrum and afterglow decay curve. The results indicated that, the phosphor was single phase ZnS and possessed hexagonal crystal structure. The light from UV to 500nm visible could excite and charge the sample. The IR sensitivity spectrum is in the range of 700—1550nm. Both the fluorescence spectrum and the infrared stimulated luminescence spectrum have two peaks corresponding to 490nm and 580nm. According to the results, the mechanism of infrared up-conversion luminescence was discussed. The energy level model of up-conversion luminescence mechanism was proposed, and the process of excitation and stimulation was analysed concretely.