Nano cuprous oxide (Cu2O) is a p-type semiconductor with abundant resources, low cost, low toxicity, and easy synthesis. Based on the narrow band gap and strong visible light absorption ability of Cu2O, Cu2O based nanocomposite materials have great potential for development in the field of photocatalysis. However, Cu2O based nanocomposite materials still face some challenges, such as easy recombination of photo generated carriers, low photocatalytic activity, easy oxidation to CuO, and poor stability. A detailed introduction to the design and synthesis strategies for Cu2O based nanocomposite materials was provided in this paper, with a particular emphasis on their applications in photocatalytic environmental protection, clean energy conversion, and antibacterial properties. To promote the practical application of Cu2O based nanocomposite materials in these fields, prospects for the next research direction have been proposed: 1) developing novel composite materials of Cu2O and non precious metal to achieve efficient and low-cost photocatalytic applications; 2) inhibiting Cu2O photocorrosion and enhancing its stability; 3) thoroughly investigating the reaction mechanism and exploring the relationship between photocatalyst structure and performance; 4) improving safety, focusing on long-term stability and biocompatibility of materials, and developing new broad-spectrum antibacterial materials.