Allylsucrose has been prepared by reaction of sucrose with allyl chloride in the NaOH-DMSO system. (DS) over bar (average degree of substitution) of allylsucrose calculated by elemental analysis was 6.7, and the efficiency of allyl chloride was 83.7%. The mechanism of the reaction was based on the acceleration of base-catalyzed reactions in dipolar aprotic solvents. The novel method is facile and suitable for large-scale preparation.