Abstract: To establish a method for determination of amino acids in Antrodia camphorata powder by HPLC with pre- column derivatization and for the evaluation of their nutritions.The samples were derived with o- phthalaldehyde( OPA).HPLC was performed on a Thermo Hypersil GOLD Dim column( 150 mm × 4.6mm,3μm) with gradient elution of 20 mmol / L sodium acetate- 0.3% tetrahydrofuran- 0.02% triethylamine( p H7.2)( A) and 100 mmol / L sodium acetate- methanol- acetonitrile( 200 ∶ 450 ∶ 350)( B) at the flow rate of 1m L / min,detected at 338.1nm. Besides,the method of ratio coefficient of amino acid was used for its evaluation of nutrition.The results showed that there were20 free amino acids and 18 combinative amino acids in Antrodia camphorata powder,which indicated that the samples had abundant amino acids.In addition to Phe + Tyr,the contents of other essential amino acids were lower than that in WHO / FAO mode.Met + cys was the first limiting amino acid.The γ- aminobutyric acid was identified in the powders,and its average content was 1.57 mg / g.