Abstract: Diethylthiophosphoryl chloride (A) was synthesized by reacting phosphorus thiochloride with anhydrous alcohol in the presence of NaOH,and then a novel phosphorus-nitrogen-and sulfur-containing flame retardant,1,4-di(O,O-diethyl thiophosphoryl imine) benzene (B),was synthesized via the reaction of diethylthiophosphoryl chloride with p-phenylenediamine.Compound B was characterized by elemental analysis,IR,¹H NMR and MS.The thermal properties of compound B were researched based on TG and DSC curves,and the influence factors such as the solvent and catalyst on the reaction rate and the yield of compound B were also studied.The thermal property studies indicate that the mass loss of compound B was 54.39% at 242.2~750℃,and when the temperature was 1 000℃,there was 25.11% char residue left,which showed that the title compound has a good thermal stability and char forming capability.Using acetonitrile as the solvent instead of trichloromethane or 1,2-dichloethane gave higher yield.During the synthesis,the yield was very low when triethylamine was used as acid acceptor alone,and when a little amount of 4-dimethylaminopyridine (DMAP) was added at the same time,the yield could be 81%.