The　first-principles　calculations　were　performed　to　investigate　the　stability,　band　structure,　density　of　states　and　redox　potential　of　Al-,　Ga-,　and　In-doped　monoclinic　BiVO4　(mBiVO(4)).　The　calculated　formation　energies　show　that　Al-doped　mBiVO(4)　inducing　an　O　vacancy　is　energetically　favorable　with　a　smaller　defect　formation　value.　With　the　incorporation　of　Al,　Ga,　and　In,　the　band　gap　of　the　doped　systems　will　be　narrowed　in　the　order　of　Al-doped　＜　Ga-doped　＜　In-doped　mBiVO(4),　which　is　beneficial　for　the　response　to　the　visible　light.　And　the　substitution　of　an　Al　or　Ga　for　a　V　atom　will　significantly　enhance　the　reducibility　of　mBiVO(4),　improving　the　efficiency　of　H-2　evolution　from　H2O.　Our　results　show　that　the　photocatalytic　activity　of　mBiVO(4)　can　be　modulated　by　substitutional　doping　of　Al,　Ga,　and　In.