A new series of photocatalysts, Bi2MNbO7 (M=Al3+, Ga3+, In3+), were synthesized by solid-state reaction and characterized by powder X-ray diffraction and Rietveld structure refinement. The substitution effect of In3+ by Al3+ and Ga3+ on the photocatalytic and structural properties of the Bi2InNbO7 photocatalyst was investigated. These photocatalysts crystallize in the same pyrochlore structure, but the lattice parameters decrease with decreasing M3+ (M3+=Al3+, Ga3+, In3+) ionic radii. The rates of H2 and O2 evolution from an aqueous methanol and cerium sulfate solution significantly increases with decreasing M3+ ionic radii under UV irradiation. The Bi2AlNbO7 photocatalyst exhibits much higher photocatalytic activity than the well-known TiO2 photocatalyst.