To research the process mechanism of Atractylodes macrocephala and conversion of sesquiterpenes from it.The contents of atractylenolide I, II and III in the different processed herbal medicines were determined by HPLC. The conversion of the sesquiterpenes was proved by the separation of oxides of atractylone.The contents of atractylenolide I and III increased after frying, and at high temperature the content of atract ylenolide III decreased. After oxidation, atractylone converted to atractylenolide I, III and biatractylenolide, and atractylenolide III converted to atractylenolide II after dehydration when heated.Atractylone can convert to atractylenolides during process of A. macrocephala, and the contents of each component are related to the level of process.