Photoelectrochemical water splitting has emerged as an effective artificial photosynthesis technology to generate clean energy of H-2 from sunlight. The core issue in this reaction system is to develop a highly efficient photoanode with a large fraction of solar light absorption and greater active surface area. In this work, we take advantage of energy band engineering to synthesize (GaN)(1-x)(ZnO)(x) solid solution nanowires with ZnO contents ranging from 10.3% to 47.6% and corresponding band gap tailoring from 3.08 to 2.77 eV on the basis of the Au-assisted VLS mechanism. The morphology of nanowires directly grown on the conductive substrate facilitates the charge transfer and simultaneously improves the surface reaction sites. As a result, a photocurrent approximately 10 times larger than that for a conventional powder-based photoanode is obtained, which indicates the potential of (GaN)(1-x)(ZnO)(x) nanowires in the preparation of superior photoanodes for enhanced water splitting. It is anticipated that the water-splitting capability of (GaN)(1-x)(ZnO)(x) nanowire can be further increased through alignment control for enhanced visible light absorption and reduction of charge transfer resistance.