ZnO/ZnS_xSe_1−x core/shell nanowires have been synthesized on n⁺-type silicon substrate via a two-step chemical vapor deposition method. Transmission electron microscopy reveals that ZnS_xSe_1−x can be deposited on the entire surface of ZnO nanowire, forming coaxial heterojunction along ZnO nanowire with very smooth shell surface and high shell thickness uniformity. The photoelectrode after deposition of the ternary alloy shell significantly improves visible light absorption efficiency. Electrochemical impedance spectroscopy results explicitly indicate that the introduction of ZnS_xSe_1−x shell to ZnO nanowires effectively improves the photogenerated charge separation process. Our finding opens up an efficient means for achieving high efficient energy conversion devices.