Hydrogen is a very promising candidate as a future energy carrier. It is attractive to produce hydrogen from solar energy and seawater, the most abundant renewable energy source and the most abundant natural resource on the earth. To date, there is no report on a stable photoelectrode with a high incident photon conversion efficiency (IPCE) in seawater splitting under irradiation by visible light. Herein, we report an efficient and stable system for seawater splitting based on a multi-metal oxide BiVO₄ after modification. The results indicated that modified BiVO₄ had a photocurrent density of 2.16 mA cm⁻² at 1.0 V_RHE in natural seawater under AM 1.5G sunlight (1000 W m⁻²) and exhibited the highest IPCE at 1.0 V_RHE in the visible light region of 440–480 nm among all known oxide photoanodes.