A preparation method for an ethanol extract of the fruiting body of Antrodia camphorata (EEAC) is provided. The preparation method includes steps of: (a) providing the fruiting body of A. camphorata (AC) (b) extracting the fruiting bodies with a first ethanol solution and (c) obtaining EEAC. EEAC further can be sequentially extracted or fractioned by n-hexane, ethyl acetate and ethanol, and an n-hexane fraction (FC), an ethyl acetate fraction (FA) and an ethanol fraction (FB) respectively are generated. The growth inhibition and apoptosis induction of leukemia cell line HL 60 are effectively mediated by FA product, in which zhankuic acid A is the bioactive marker. The amount of triterpenoid in the fruiting body of AC can be determined by NMR and HPLC analysis.
