Macromolecules may be affected by high pressure treatment,such as starch,protein and polysaccharides.Soybean dietary fiber was processed by instantaneous high pressure at 140Mpa,the samples before and after this treatment were named A and B respectively.The No.6890 Agilent GC was used to detect the monosaccharide components.The working parameters were listed as follows:Injector temperature,280 ℃; the temperature program was set as 160℃ for 2min,160℃-240℃(10℃/min),240℃ for 15min; column temperature,220℃; FID detector,260℃; split ratio,1∶20 and 1∶5; flow of N2,2.1ml/min;flow of H2,30ml/min; flow of air,400ml/min.Six kind of standard monosaccharide were mixed as a guide sample,which were Rhamnose,Arabinose,Xylose,Mannose,Glucose and Galactose respectively.