This paper analyzes the origin and evolution of the idioms in Huainanzi from the historical dimension and helps the in-depth research of the history of Chinese idioms.Based on the characteristics of idiomaticity,constancy,com-pleteness and double-layeredness of meaning,331 idioms in Huainanzi are counted,including 211 idioms from pre-Qin or earlier literature of the same period,and 120 idioms from Huainanzi.The derivation and usage category of Huainanzi idioms was formed by eight methods,such as direct quotation,word replacement,word reduction,condensation,a-bridgement and merger,consolidation,sequencing and synthesis,while the original ones were transformed into idioms in the later times by five ways:intercepting phrases,changing phrases or sequences,adding phrases,and summarizing sto-ries or condensing phrases.The evolution of idioms in Huainanzi mainly focused on the evolution of form and meaning:the former including changes in the internal morphemes and word order of idioms,and the latter including the evolution of rational meaning and color meaning.