In this paper, we report the investigation of photoluminescence (PL) characteristics of ZnS nanocrystals doped with M3+(M = In, Ga and Al). X-ray diffraction analysis shows that the diameter of the particles is 2.6 +/- 0.2 nm. The nanoparticles can be doped with M3+ (In, Al, Ga) ions during synthesis without altering the X-ray diffraction pattern rind the emission wavelength (440 nm) of the samples. However, the fluorescence efficiencies are varied with the variation of doping mole ratio of In3+. The relative fluorescence intensity of In3+-doped sample is about 1.5 times of that of ZnS nanocrystallites.