Abstract: Centrifuge,micro porous filter membrane,and ultrafiltration-nanofiltration were used to separate,filter,and concentrate the enzymatic hydrolysis solution of konjac for preparing konjac oligosaccharides. Soluble glycan filtrates of 150 g/L filtered through the ultrafiltration membrane and the oligosaccharides recovery rate could reach over 86%. The filtration flux of the nanofiltration membrane decreased with the concentration of soluble glycan increasing. The matrix-assisted laser desorption ionization-time of flight mass spectrometer(MALDI-TOF-MS)used to analyze 100~5000 Da konjac oligosaccharides mixtures. The results showed that the content of trisaccharide was the highest single component with 21.5%,the total content of disaccharides to(C₆H₁₀O₅)₁₄ reached 90%,and(C₆H₁₀O₅)₁₅~(C₆H₁₀O₅)₂₀content was 9%. It was feasible to use membrane filtration technology in the separation,purification and concentration of konjac oligosaccharides.