Abstract: Oxide semiconductor photocatalytic technology is one of the effective methods to solve the problem of water pollution and energy shortage. Compared with other metal oxide semiconductors, cuprous oxide has many advantages, such as non-toxicity, good environmental acceptability, low price and high activity, which have led to a great deal of research on this material in the past decades. Researchers prepared cuprous oxide and its composites by liquid phase, solid phase and gas phase methods, respectively. The photocatalytic activity and photostability of cuprous oxide were improved by adjusting the morphology of the synthesized samples, increasing the exposure degree of the active crystal plane, building layered structure and heterojunction structure, and increasing the specific surface area. That has promoted the application of cuprous oxide in many fields, such as photocatalytic degradation of dyes, solar cells and hydrogen production. In the preface of this paper, the main shortcomings of cuprous oxide are discussed to point out that the synthesis of cuprous oxide with different morphologies, sizes and structures has an important effect on its properties. In the main part, the main preparation methods and their advantages and disadvantages are introduced, and the main research focus and progress of the researchers are reviewed. In the conclusion part, the future research direction is prospected according to the unsolved research problems of cuprous oxide.