Abstract: Cuprous oxide (Cu₂O) has become a key photocathode material in the field of photoelectrochemical (PEC) hydrogen production due to its unique band structure, excellent photoresponse performance and economic cost. However, its REDOX potential is located in the band structure, and it is easy to be photoinduced bidirectional corrosion in aqueous solution, which affects its stability and performance. Therefore, researchers are committed to developing various strategies to enhance the performance of Cu₂O stability. This paper systematically reviews the surface modification, doping and other modification methods, to accurately regulate the surface properties of Cu₂O, optimize the electronic structure or introduce heterogeneous elements, significantly improve its photocorrosion resistance, and thus enhance stability. These improvements not only consolidate the basic performance of Cu₂O, but also directly promote the optimization of its hydrogen production performance, and show that stability is positively correlated with hydrogen production efficiency. In addition, the paper highlights the importance of establishing a unified Cu₂O photocathode stability test standard to ensure repeatability and comparability of studies, facilitate testing in simulated real-world application scenarios, and provide reliable data and theoretical guidance for optimal design, modification strategies, and future commercial applications.