The crude dextran was separated and purified from the mixed juice ( MJ) of sugarcane through ethanolprecipitation,enzymatic hydrolysis and ultrafiltration,and the corresponding relative molecular mass distributionwas characterized by means of GPC. Then,dextranase was used to hydrolyze the dextran in the MJ,and the changelaws of the relative molecular mass and concentration of dextran during the enzymatic hydrolysis were investigated bymeans of GPC and IC.The results show that (1) the relative molecular masses of the dextran in the MJ stored atthe room temperature for 20h are mainly 1.02 × 106 and 3.57 × 103 ; (2) the relative molecular mass of the dextransignificantly decreases with the extension of the reaction time; (3) dextranase can hydrolyze the dextran into theoligosaccharides，which are the final major products; and (4) the concentration change of dextran is related to thecorresponding relative molecular mass change.