Abstract: Proper conditions for the esterification reaction of starch with maleic anhydride were presented after examining the effects of several factors such as reaction temperature,reaction time,the ratio of reactants and water content on the degree of carboxylation (DC) and the degree of substitution (DS) of the product.With 6 mL of pyridine as the catalyst,6 g of starch were reacted with 6 g of maleic anhydride in the mixed solvent of 7 mL of water and 30 mL of N,N-dimethylformamide at 30℃ for 9 h,and the starch-half-ester was obtained.It was found that DC and DS of the starch-half-ester were 34.7% and 0.868,respectively.In addition,the carboxylic derivate of the starch was prepared through an alternative route.Initiated with 1.5 g K₂S₂O₈,12 g of starch were allowed to react with 10 g of maleic acid in 30 mL of water at 95℃ for 4 h.DC and DS of the derivate were 42.7% and 1.22,respectively.The structures of the two derivates were verified with FTIR.The X-ray diffraction analysis results show that the crystallinities of the two derivates are lower than that of starch.