An improvement method of sucralose synthesis yield, it takes azo reagent as catalyst, acetic acid as acylating reagent and synthesizes the cane sugar into sugar-6-acetate under proper dissolvent; then the sugar-6-acetate and proper chlorinated reagent are synthesized into sucralose-6-acetate under non-proton polar solvent with TCA as catalyst. At last, the alcoholysis of sucralose-6-acetate is completed in KOH/methanol system and then the product sucralose is synthesized. With the advantages of mild reaction conditions, high selectivity, high yield rate, and brief operation etc., the invention is prone to industrial production.