Nanocrystalline　ZnS　particles　were　prepared　by　hydrothermal　method　and　characterized　by　XRD,　FT-IR,　TEM　and　UV-vis　DRS　and　their　photocatalytic　activities　were　evaluated　by　the　photodegradation　of　Eosin　B　under　visible　light.　The　results　showed　that　the　ZnS　nanoparticles　we　prepared　were　in　hexagonal　phase,　their　average　size　of　the　complex　particles　varies　from　10　nm　to　20　nm,　and　also　revealed　well　photocatalytic　activity　under　visible　light,　the　photocatalytic　decolouration　rate　of　Eosin　B　in　3　h　reached　70　%.