Broader visible light response, higher carrier separation efficiency and injection efficiency are extremely important methods to enhance photoelectrochemical (PEC) performances of WO₃. In this work, FeOOH with the property of storing holes is firstly applied to modify WO₃/Cu₂O heterojunction as an interlayer, and the WO₃/FeOOH/Cu₂O ternary heterojunction with excellent PEC performances is obtained. The separation efficiencies of photoinduced carrier in bulk is enhanced to 29.33% with the formation of dual built-in electric filed as well as the storage of photoinduced carriers transferred from WO₃ in FeOOH, which is 3.27 folds higher than that of bare WO₃. With the synergistic effect of expanded light absorption and accelerated charges transfer, the photocurrent density of 2.14 mA/cm² at 1.23 V vs. RHE is achieved by WO₃/FeOOH/Cu₂O ternary heterojunction. This work can be applied for reference to improve the PEC performance of other photoelectrodes through adequate utilization of storing holes interlayer.