Green phosphors K2BaW2O8:Tb3+(1.0mol%) were synthesized by solid state reaction method. Differential thermalanalysis was applied to trace the reaction processes. Three endothermic values of 95, 706, and 1055oC correspond to the lossof absorbed water, the release of carbon dioxide, and the beginning of the melting point, respectively. The phase purity of thepowders was examined using powder X-ray diffraction(XRD). Two strong excitation bands in the wavelength region of 200-310nm were found to be due to the WO42− exciton transition and the 4f-5d transition of Tb3+ in K2BaW2O8. The excitationspectrum presents several lines in the range of 310-380nm; these are assigned to the 4f-4f transitions of the Tb3+ ion. The strongemission line at around 550nm, due to the 5D4→7F5 transition, is observed together with weak lines of the 5D4→7FJ(J=3,4, and 6) transitions. A broad emission band peaking at 530nm is observed at 10K, while it disappears at room temperature.The decay times of Tb3+ 5D4→7F5 emission are estimated to be 4.8 and 1.4ms, respectively, at 10 and 295 K; those of theWO42− exciton emissions are 22 and 0.92µs at 10 and 200K, respectively.