A novel approach for identifying acetone using Raman spectroscopy and three-hole microstructure optical fibers (MOFs) is reported.This technique comb ines the advantages of the specificity of Raman spectroscopy and the small sampling v olume of MOF (nano liter).Acetone solution goes into the air-holes of MOF by capilla ry effect,the Raman signal is generated by the excitation of evanescence wave in the air-hol es and the acetone concentration is detected by measuring the Raman signal intensit y coupled back to the core of the MOF.The solvent′s Raman signature is used as an internal calibration standard.The Raman intensity ratio between C-H stretching peak of acetone at 2843cm－1 and H-O stretching peak at 3371cm－1 of water is used to detect the concentration of acetone.The experimental results show that when the acetone concentration increases from 5% to 50%,the ratio between C-H stretching peak of acetone and H-O stretching peak of water increases linearly,and their correlati on coefficent is 0.98.This system can also be used to analyze other votilate organ ic compounds qualitatively and quantitatively.