BiTa1 xN bx O4 (0≤x≤1) solid photocatalysts were prepared by solid-state reaction and characterized by powder X-aydiffractionand Rietvel dstruc turerefin ement.Thestru cture of Bi Ta1-xNbxO4 (x=0.0 and 0.5) istriclinic. However, the structures of x=0.2, 0.8 and 1.0 are or thor hombic. The H2 evolution was obtained from an aqueous CH3OH/H2O solution and from pure H20 with Bi Ta1-xNbxO4 (0≤x≤1) under UV irradiation. The orthorhombic photocatalysts exhibit much higher activity than that of triclinic photocatalysts. The orthorhombic photocatalyst at x=0.2 showed the highest activity. An UV vis diffuse reflectance spectroscopy measurement revealed that the band gap of orthorhombic photocatalysts is more narrow than that of triclinic photocatalysts.