Abstract: The recent progress in processing, microstructure and properties of medium entropy alloys based on CoCrNi was reviewed.The specific situation of mediumin entropy CoCrNi base alloy was introduced, including the related concepts of high entropy alloy and medium entropy alloy, and the application prospect and application field of entropy alloy in CoCrNi base. The research on processing technology, microstructure and mechanical properties were introduced. The problems existing in the study of the alloy were summarized, and the future research direction of the medium entropy alloy in CoCrNi base was prospected.