A high-entropy oxide is a single structural oxide formed from a solid solution of a variety of metal or nonmetal oxides in equal or nearly equal proportions and has wide application prospects in the field of energy. This paper mainly introduces the advantages of high-entropy oxides (cocktail effects, high-entropy effects, lattice distortion effects, etc.) and synthesis methods, which mainly include the high-temperature solid-phase reaction method, pyrolysis method, coprecipitation method, solution combustion synthesis method, and hydrothermal synthesis method, and on the basis of their excellent performance in catalytic hydrogen production, supercapacitors, lithium batteries and other electrochemical energy storage applications. The research progress on high-entropy oxides in the field of electrochemical energy storage is reviewed.