The fluorescent spectra of the phosphors CaS∶Ag prepared rapidly by microwave radiation method are studied. The XRD analysis shows that the structure of the phosphors belongs to cubic system. The SEM photographs show that all the CaS∶Ag phosphors possess spherical shapes, but the effect of different fluxes and silver concentrations on crystal size and distribution is different, they are nano-scale (7～100 nm) and submicron-scale (125～300 nm) crystallines. The excitation and emission spectra of the phosphors CaS∶Ag are measured and explained. In emission spectra, three peaks located at 372 nm, 450 nm and 577 nm have been observed, respectively. With different fluxes and with different silver concentrations, the emission spectra of CaS∶Ag phosphors change complicatedly. The peak of 372 nm is produced by AYg′ Ca-V 2 S centers. The peak of 450 nm migrates to shorter wavelength with the increase of silver concentrations. It is caused by interstitial Ag ions. The peak of 577 nm is quenched by increase of silvr concentrations. It is caused by interstitial Ag+ ions. The peak 577 nm is quenched by increase of silver concentrations. It is produced by substitutive Ag+ ions and fundamental emission of CaS. In addition, the good distribution of crystal attributes to the increase of Iblue/Iyellow. During the preparation of CaS:Ag+ in microwave field, three colors powders have been obtained. They are white powder, light gray and brown. The quantitative analysis based on their XRD experimental data shows that the microwave reaction mechanism is that the diffusions of ions in the microwave field are enhanced.