With unique multi-principal element alloy system, medium and high entropy alloys exhibit a series of outstanding comprehensive properties: not only do they possess high strength and hardness, but they also have strong wear resistance and good chemical stability. In high-temperature environments, medium and high entropy alloys can still maintain stable structures and properties, and have excellent oxidation resistance. These properties make them widely used in aerospace, electronic processes, mechanical engineering and other fields. Due to the precise formula and uniform mixing of multiple elements involved in preparation of medium and high entropy alloys, there are extremely high requirements for purity of raw materials and accuracy of composition contents. At the same time, during the smelting process, in order to prevent problems such as composition segregation and non-uniform microstructure in medium and high entropy alloys, it is necessary to precisely control smelting parameters to ensure uniformity of the alloy composition and stability of the microstructure. This review sorted out a large number of domestic and international literatures. It summarized composition design of medium and high entropy alloys, and discussed preparation process of medium and high entropy alloy coatings and influence of process parameters on coating quality, providing references for innovation in material composition and structure of medium and high entroply alloy coatings.