Abstract: A novel synthesis of Sinomin by the 1,3-dipolar addition of nitrile oxide was reported. The 1,2,3-trichlorobutylaldehyde oxime (Ⅰα) was converted into 1,2-dichloropropylnitrile oxide (Ⅱα) on action of sodium methoxide. (Ⅱα) was treated with p-acetaminobenzenesulfamide, then the addition product was converted to 3-(p-acetaminobenzenesulfanilylamide-5-methylisoxazole(ASMZ) (Ⅲα) through cycli-zation and elimination in situ. The 3-(p-aminobenzenesulfanilylamido)-5-methyl-isoxazole(SMZ) (Ⅳα) was obtained when ASMZ was heated to 120℃ in 20% sodium hydroxide solution for 2 hr.In the same way the 3-(p-aminobenzenesulfanilylamido)-5-phenylisoxazolc (SPZ) (Ⅳb) was prepared.