Photoelectrochemical (PEC) hydrogen production from water splitting is a green technology to convert solar energy into renewable hydrogen fuel. The construction of host/guest architecture in semiconductor photoanodes has been proven to be an effective strategy to improve solar-to-fuel conversion efficiency. In this study, WO₃@Fe₂O₃ core-shell nanoarray heterojunction photoanodes are synthesized from the in-situ decomposition of WO₃@Prussian blue (WO₃@PB) and then used as host/guest photoanodes for photoelectrochemical water splitting, during which Fe₂O₃ serves as guest material to absorb visible solar light and WO₃ can act as host scaffolds to collect electrons at the contact. The prepared WO₃@Fe₂O₃ shows the enhanced photocurrent density of 1.26 mA cm^-2 (under visible light) at 1.23 V vs RHE and a superior IPEC of 24.4% at 350 nm, which is higher than that of WO₃@PB and pure WO₃ (0.43 mA/cm^-2 and 16.3%, 0.18 mA/cm^-2 and 11.5%) respectively, owing to the efficient light-harvesting from Fe₂O₃ and the enhanced electron-hole pairs separation from the formation of type-II heterojunctions, and the direct and ordered charge transport channels from the one-dimensional (1D) WO₃ nanoarray nanostructures. Therefore, this work provides an alternative insight into the construction of sustainable and cost-effective photoanodes to enhance the efficiency of the solar-driven water splitting.