Propylene oxide is one of important building blocks in chemical industry. Until now, the major conventional manufacturing methods of propylene oxide are the chlorohydrin and the Halcon processes. The chlorohydrin process is phase-out due to environmental pollution, while the latter has the byproduct limitation. The most ideal process is the epoxidation of propylene with molecular oxygen as the oxidant to produce propylene oxide; however the reaction remains one of the biggest challenges in the catalysis field. Propylene epoxidation by oxygen on Cu-based catalysts is just beginning, and until now the relative reports are very few. The green catalytic synthesis of propylene oxide on Ag, TS-1/H₂O₂, and Au is simply introduced. The advantages and disadvantages as well as industrial application prospect of these systems are discussed, respectively. Then, the recent progress in propylene epoxidation by oxygen over Cu catalysts is detail reviewed. The influence of Cu catalysts preparation methods, alkali metal ions promoters, and metal cocatalysts on the catalytic performances of propylene epoxidation by oxygen is outlined. Finally, the prospects in the field are presented.