Abstract: With the N and N-dimethylformamide as reaction medium,N-maleoyl chitosan was synthesized by microwave irradiation.Effects of the mole ratio of maleic anhydride to chitosan,microwave power,microwave irradiation time and reaction temperature on the degree of substitution were investigated by using single factor experimentation and orthogonal experimental design.The optimal condition for the reaction of N-maleoyl chitosan by microwave is:the microwave power(600w),the temperature(110℃),the time(25min) and the mole ratio of maleic anhydride to chitosan(1.5:1).The characteristic absorption bands in IR and the change of the strong absorption bands in UV both show the structure of N-acyl chitosan.The study of elemental analysis confirms that maleic anhydride successfully modifies the chitosan.