CaS∶Cu+,Cl- phosphor of blue luminescence was prepared by solid phase reaction at high temperature to be with calcium sulfate(CaSO4·2H2O)and charcoal (C powder) as raw materials and copper sulfide(CuSO4) or sub-copper sulfde(Cu2S) as an activator.Effects of the activator concentration,reaction atmosphere,and reaction time on luminescence characteristics of the product were tested in detail.Fluorescent properties tests show that CaS∶Cu+,Cl- can effectively absorb ultraviolet light of 240-350 nm and emit blue luminescence of semi-peak width 60 nm,main peak 434nm.Blue light is in need of plant photosynthesis and the luminescence belongs to emission of Cu+ 3d94s1→3d10 transition.