A　series　of　ZnIn2S4　floriated　microspheres　consisting　of　flakes　were　synthesized　by　a　facile　template-free　hydrothermal　method.　The　obtained　ZnIn2S4　products　were　characterized　by　X-ray　diffraction,　scanning　electron　microscopy,　high-resolution　transmission　electron　microscopy,　energy-dispersive　X-ray　spectroscopy,　UV-vis　diffuse　reflectance　absorption　spectroscopy,　and　nitrogen　adsorption　measurement.　The　effects　of　hydrothermal　temperature　and　pH　value　on　the　crystal　structures,　morphologies,　and　optical　properties　of　ZnIn2S4　microspheres　were　investigated.　The　photocatalytic　activities　for　hydrogen　production　of　the　as-prepared　samples　were　evaluated　under　visible-light　(λ≥　420　nm)　irradiation.　It　was　found　that　the　1.0　wt　%　Pt-loaded　ZnIn2S　4　prepared　hydrothermally　at　160　°C　with　pH　=　1.00　showed　a　higher　and　steady　photoactivity　for　H2　evolution　from　aqueous　solutions　containing　sacrificial　reagents　SO32-　and　S　2-　than　the　products　prepared　at　other　hydrothermal　temperatures.　Moreover,　an　apparent　quantum　efficiency　of　up　to　34.3%　was　achieved　under　incident　monochromatic　light　of　420　nm,　significantly　higher　than　previously　reported　values.　©　2011　American　Chemical　Society.