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(mBiVO4). The calculated formation energies show that Al-doped mBiVO4 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 mBiVO4, 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 mBiVO4, improving the efficiency of H2 evolution from H2 O. Our results show that the photocatalytic activity of mBiVO4 can be modulated by substitutional doping of Al, Ga, and In. 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 (mBiVO4). The calculated formation energies show that Al-doped mBiVO4 inducing an With the incorporation of Al, Ga, and In, the band gap of the doped systems will be narrowed in the order of Al-doped