Abstract: A long-lag luminescent material CaS:Eu²⁺,Tm³⁺ is prepared with high temperature solid phase synthesis technique. The phase of the material is analyzed by using XRD and the excitative and emissive wavelength are detected on phospher luminometer. The optimum concentrations of Eu²⁺ and Tm³⁺ and the optimum sintering temperature of 1150℃ are determined. The effects of some additive agents on luminescent performance is also covered.