Abstract: Dialdehyde starch was prepared by the method of acid hydrolysis and oxidation, in which corn starch as raw material, hydrochloric acid as acid agent and sodium periodate as oxidant. The effect of concentration of hydrochloric acid, reaction temperature and reaction time on the aldehyde content of dialdehyde starch was considered by orthogonal experiment. The process of acid hydrolysis and oxidation was optimized with response curve analysis, interaction analysis and significant analysis. The results showed that the order of factors influencing aldehyde content of dialdehyde starch was reaction temperature, reaction time, concentration of hydrochloric acid. The optimum condition was that the concentration of hydrochloric acid was 0.9 mol/L, the reaction temperature was 55 ℃ and the reaction time was 2 h. And aldehyde content of dialdehyde starch prepared for the optimum conditions was 69.56%.