ZnS nano-microcrystallites with different size were controllably synthesized by a facile homogeneous precipitation method. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, N-2-sorption BET surface area and UV-vis diffused reflectance spectra for their morphology, size and optical performance. Results show that the crystallinity and size of the samples strongly depend on the Zn/S molar ratio of the precursor solution. Moreover, the electronic band structures of all samples were investigated relatively from the sides of theory and practice. The photocatalytic performances of the as-prepared ZnS samples were evaluated towards the removal of MO upon UV-light irradiation. The results indicate that the ZnS nanoparticles prepared at the Zn/S molar ratio of 1:2 exhibited the highest photocatalytic activity with the degradation ratio of 96.8% in 24 min, which was mainly attributed to the high separation efficiency of electron and hole pairs and large surface area. With the help of scavengers, center dot O-2(-) was proved to be the main reactive species during the degradation. (C) 2016 Published by Elsevier B.V.