Abstract: Polysaccharides of Dioscorea fordii Prain et Burkill were extracted by hot water and alkali succeededly.The polysaccharide in the filtrate were precipitated by ethanol. The protein in the product were removed by means of trichloroacetic acid followed twice by Sevage method. The polysaccharide was decoloured by active carbon, then purified twice by Sephadex G-75 column chromatography to obtain the homogeneous polysaccharide DFPN-Ⅰand DFPA-Ⅰ, and their homogentity were examined with paper chromatography, polarimetry and molecular weight determination. The units of monosaccharides of DFPN-Ⅰ were identified by paper chromatography and gas chromatography to be mannose, glucose, galactose at ratio 1.26:1.00:2.87 after complete hydrolysis by acid. Similarly, the monosaccharides of DFPA-Ⅰ were identified to be mannose, glucose, galactose, galacturonic acid at ratio 2.18:1.00:3.39:1.82in combination with determination of content of uronic acid.