Abstract : La doped ZnS nanopowder was synthesized by co precipitation method. In FTIR spectra, the major peak at 676 cm-1 and 661 cm-1 was due to Zn-S stretching bond. Crystallite size was calculated by effective mass model from UV absorption data, Scherer formula and W-H plot and found to be almost same. The crystallite size lies between 1 to 5 nm indicating quantum confinements. Dislocation density was observed to be decreased in case of ZnS: La0.5 mol%. This might be due to the higher growth in crystallite size. Board emission peak was observed at 489nm which conclude the utilization of nanophosphor for display devices