Bismuth vanadate (BiVO₄, BVO) as a promising photoelectrode has been received great attention for photoelectrochemical (PEC) water splitting. However, the slow oxidation kinetics on the surface of BiVO₄ limited the PEC water splitting efficiency. Herein, nickel boride (Ni₃B, NB) nanoparticles, generally used in electrocatalytic field material, were modified on the surface of BiVO₄ photoelectrode as an efficient cocatalyst to accelerate the oxygen evolution reaction. The as-prepared BVO-NB-5P photoelectrode exhibits a remarkable photocurrent density of 1.47 mA·cm⁻² at 1.23 V versus the reversible hydrogen electrode (RHE) under air mass (AM) 1.5 G illumination, which is about 2.8 times higher than the bare BiVO₄ photoelectrode, and its water splitting rate is 11.3 times higher than bare BiVO₄. The PEC studies reveal that the spin coated Ni₃B crystal cocatalyst could effectively reduce the water oxidation barrier, and improve the surface charge injection efficiency to 94%, which could boost the photogenerated holes reaction to enhance the PEC performance of BiVO₄ photoelectrode.