Abstract: Organic acids in Xihu tobacco were derived into methyl esters by using boron trifluoride etherate and methanol, and extracted with dichloromethane. Furthermore, the methyl ester derivatives of the acids were determined qualitatively and quantitatively by gas chromatography/mass spectrometry. 41 organic acids components were identified in total, the main compounds in tobacco included hydroxylbutanedioic acid (47.82%), citric acid(14.71%), 9,12,15-octadecatrienoic acid(7.50%). The proposed method is simple, rapid and results are satisfying.