Dialdehyde starch-aniline Schiff-base (DAS-AN) was synthesized with dialdehyde starch (DAS) and aniline as reactants, and acetic acid as catalyst in dimethyl sulfoxide (DMSO) homogeneous system under N2 atmosphere. The synthesis conditions of DAS-AN were studied and the optimum conditions were as follows: the mass concentration of DAS is 100 g/L in DMSO, the dosage of acetic acid is 3% (volume), reaction temperature is 50℃, the molar ratio of aldehyde group to amino group is 2:1, and reaction time is 12h. Under the optimum conditions, the utilization ratio of aniline is 94% with DAS5 (the dialdehyde content is 5%) as reactant, and that is 55% with DAS20 (the dialdehyde content is 20%) as reactant. The structure of DAS-AN is characterized by FT-IR, NMR and XRD.