Nanocrystalline　In(OH)(y)S-z　solid　solutions　were　synthesized　from　In(NO3)(3)　and　thiourea　in　an　aqueous　solution　of　ethylenediamine　via　a　facile　hydrothermal　method.　The　samples　were　characterized　by　X-ray　diffraction　(XRD),　N-2-sorption　(BET　surface　area),　UV-vis　diffuse　reflectance　spectra　(DRS),　transmission　electron　microscopy　(TEM),　high-resolution　transmission　electron　microscopy　(HRTEM),　energy　dispersive　X-ray　spectra　(EDS),　and　X-ray　photoelectron　spectroscopy　(XPS).　The　position　of　the　valence　band　for　In(OH)(y)S-z　was　established　by　ultraviolet　photoelectron　spectra　(UPS).　Electronic　band　calculations　based　on　density　functional　theory　(DFT)　revealed　that　upon　being　doped,　several　doping　states　derived　from　S　3p　orbitals　appeared　in　the　band　gap　of　undoped　In(OH)(3).　In(OH)(y)S-z　showed　visible-light-driven　photocatalytic　activity　in　the　decomposition　of　gaseous　acetone.　A　possible　sub-band-transition　mechanism　of　the　photocatalysis　on　In(OH)(y)S-z　solid　solutions　under　visible　light　irradiation　was　also　proposed　in　this　work.