CaS: Ce3+, Sm3 + optical storage material was prepared by wet-method under the reducing atmosphere. Influence of sintering atmosphere on luminescence intensity was studied to get the result that active-carbon reducing atmosphere is better. XRD analysis shows that CaS crystal structure was formed at 700 ℃. The excitation spectrum is in the range of 250 ～ 500 nm with peaks at 260.2, 353.4 and 461.2 nm, the fluorescence spectrum shows a broadband spectrum with peaks at 503, 568 and 604 nm and the emission spectrum of the sample stimulated by 980 nm laser also shows a broadband spectrum with peaks at 508,565 and 600 nm. The result of spectra analysis indicates that this material can absorb and "trap" incoming light energy from ultraviolet and visible light (Information write-in), and release that stored energy in the form of green luminescence (information read-out) upon stimulation from a longer IR wavelength. The optical storage physical mechanism was also discussed.