Enormous efforts have been made to search suitable photocathode materials for photoelectrochemical (PEC) system, because it is a promising way to directly convert solar energy to H₂, to meet the urgent demand for global energy. Among common photocathode materials, earth abundant p-type Cu₂O is one of the most promising candidate due to its bandgap (2 eV), which facilitates visible light absorption, and its suitable conduction band (0.7 eV) which is negative of hydrogen evolution potential. But its poor stability in aqueous solution severely restricts its application in PEC system. To solve this problem, we adopt a simple and convenient method to form the ultrathin carbon film which has the outstanding electrical conductivity to transfer photogenerated electron from semiconductor into electrolyte solution to protect Cu₂O from self-photocorrosion. It was found that carbon based catalyst with ultra-high hydrogen evolution reaction catalytic activity serves as an important role to enhance photocurrent density. This work provided a low cost and simple synthetic method for improving the stability of Cu₂O planar film and efficiency of water splitting. This available strategy could expand to design many other materials which endure stability problem in PEC system, and the carbon based catalyst/carbon film/Cu₂O multilayer structure might be the model system for basic research of designing other high-performance photocathode materials.