Sodium diacetate was synthesized from sodium acetate trihydrate and acetic acid without any solvent. The effects of the component ratio, reaction temperature, time and water content on the product yield and quality have been discussed and the optimum technological conditions have been obtained. The optimum conditions by orthogonal design were determined as follows:the ratio of acetic acid to sodium acetate trihydrate 1.1∶1(molar), reaction time 30min,water content 10%.The product quality was up to FAO standard and the yield over 96%.