Novel FeVO4/Bi7O9I3 nanocomposites with different weight percentages (3, 6.25, 12.5, and 25%wt) of FeVO4 were successfully synthesized by cyclic microwave irradiation, followed by wet impregnation. The applications for photocatalytic dye degradation and photoelectrochemical (PEC) were investigated. The 6.25%wt-FeVO4/Bi7O9I3 nanocomposite exhibited excellent photocatalytic degradation of methylene blue, rhodamine B, and methyl orange with decolorization efficiencies of 81.3%, 98.9%, and 94.9% within 360 min, respectively. Moreover, this nanocomposite possessed excellent reusability and stability during the photocatalytic degradation process. PEC performance in water oxidation of the 6.25%wt-FeVO4/Bi7O9I3 photoanode was evaluated by linear sweep voltammetry (LSV) measurement. Enhanced PEC performance with photocurrent density of 0.029 mA cm(-2) at 1.23 V (vs. RHE) was observed under visible-light irradiation, which was ca. 3.7 times higher than that of the pure Bi7O9I3. Based on the optical characterization, energy band positions, and active species trapping experiments, a possible photocatalytic mechanism of the FeVO4/Bi(7)O(9)I(3 )heterojunction was discussed. The enhancement in the photocatalytic and the PEC performance ascribed to synergistic effects of visible-light absorption and a favorable "type II heterojunction" structure of the FeVO4/Bi7O9I3 nanocomposite. These were the main effects that promoted the photogenerated electrons and holes transfer across the contact interface between FeVO4/Bi7O9I3, as well as suppressed the recombination of photogenerated electron-hole pairs and facilitated charge separation and transportation.