A method for the simultaneous determination of three main keto ageing compounds,such as diacetyl,2,3-pentanedione and β-damascone,in beer by dispersive liquid-liquid microextraction/high performance liquid chromatography was proposed.Derivatization conditions of diacetyl and 2,3-pentanedione and high performance liquid chromatography conditions of the three target components were established.The separation and detection of three keto ageing compounds were performed in 15 min.The conditions of dispersive liquid-liquid microextraction were studied,and the enrichment factors of three compounds were 45,63 and 121,respectively.Good linearities were obtained for three compounds with correlation coefficients of 0.999 6-0.999 9,and the linear range is greater than or equal to 103.The detection limits(S/N=3) were in the range of 0.3-0.9 μg/L.The average recoveries of real samples were in the range of 86%-97% with RSDs of 2.4%-4.8%.