Abstract: By gas chromatographic headspace analysis,a highly sensitive and simplified mothod for the determination of blood ket one has been studied.Acet oacetate and beta-hydroxybutyrate are made a linear standard curve by using aceton area,and correlation cofficient is 0.997 and 0.990 respectively,The relative standard deviation (RSD)is no more than 9.3%.The blood ket one body ratio is a great help to climcal diagnosis.