Photocatalysis became one of the important ways to solve the current global crisis and environmental pollution in recent years. It uses the solar energy to product hydrogen via water splitting or to degenerate the organic pollutants, which is not only low-lost but also environmentally friendly. Cu2O is a p-type semiconductor oxide with the band gap of 2.0~2.2 eV based on its size and shape. Therefore Cu2O can adsorb the visible part of the sunlight and has a potential application in the photocatalytic field. In this review, we introduced the details of Cu2O structural characteristics, which contains two interpenetrating three-dimensional Cu2O networks and special band structure. Then, the modification investigations of Cu2O including doping and coupling are described. Further more, the researches on the water splitting and the degeneration of organic compounds using the Cu2O and modified Cu2O photocatalysts are discussed. The keys which inhibit the photocatalytic efficiency of Cu2O are the recombination of the photo-excitated electrons and holes as well as the photo corrosion of Cu2O. In the end, the ideas for further research were presented based on the problems of Cu2O as the photocatalyst.