Bismuth vanadate is a promising photoanode material for photoelectrochemical (PEC) water splitting, but its activity and stability need to be further improved. In this work, we synthesized Ni-doped BiVO4 abundant with V4+ species and oxygen defects through an in situ electrodeposition method. The effective doping can decrease the particle size of BiVO4 and lead to the formation of V4+ species/oxygen defects. Accordingly, the doped and defective BiVO4 showed high optical absorption and rapid charge transfer, and further showed much higher PEC activity than pure BiVO4. Specifically, 5-Ni-BiVO4 exhibits the highest activity in PEC water splitting, with a photocurrent of 2.39 mA/cm2 at 1.23 V versus RHE (the reversible hydrogen electrode), which is 2.5 times higher than pure BiVO4 (0.94 mA/cm2), and much higher incident photon-to-current efficiency (IPCE) value of 45％ (while only 25％ for BiVO4 at ca. 400 nm). This work provides an in situ method for the development of a high-performance photoanode.