The effects of Zn precursors, S precursors and hydrothermal temperatures on the morphologies and structures of ZnS microspheres were investigated by a facile hydrothermal method. The results showed that the mixed phase ZnS microspheres prepared with ZnCl₂ and L-cysteine at 180 °C exhibited a visible light response. The as-prepared ZnS microspheres were used for photodegradation of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB). The photodegradation rates of ZnS microspheres to these azo dyes were 87.5% (RhB), 84.3% (MB), and 65.3% (MO), respectively. In addition, ZnS microspheres maintained good photodegradation activity after four cycles. In this work, ˙O₂⁻ was the major active species and the possible photocatalytic mechanism of ZnS microspheres was also illustrated.