Hematite is a prospective semiconductor in photoelectrochemical (PEC) water oxidation field due to its suitable bandgap for the solar spectrum absorption. Nevertheless, the low transfer and separation efficiency of the charge carriers are restricted by its diffusion length of hole which is 2-4 nm and further reduce the PEC performance. Here, we report an innovative method, by introducing nanocavities into the alpha-Fe2O3 nanorod arrays photo anodes through helium ions implantation, to improve the charge carriers' transfer and separation efficiency and further to enhance water oxidation performance. The result in dicates that, the photocurrent density of nanocavities embedded alpha-Fe2O3 photoanode (S2-A sample) reaches 1.270 mA/cm(2) at 1.6 V vs. RHE which is 1-fold higher than that of the pristine alpha-Fe2O3 (0.688 mA/cm(2)) and the photocurrent density of S2-A sample reaches 0.652 mA/cm(2) at 1.23 V vs. RHE. In this work, the ion implantation combined with post annealing method is found to be a valid method to improve the photoelectrochemical performance, and it also can be further used to modify the other semiconductor photoelectrodes materials. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.