1,2-ethylene bis(dimethyl Phosphonate) was synthesized by trimethyl phosphite and 1,2-dibromoethane, using tetramethyl ammonium iodide as catalyst. It’s a kind of flame retardant which is environment-friendly and halogen-free. The optimal reaction conditions were obtained: the reaction temperature 160 ℃, the reaction time 4.0 h ,the ratio of trimethyl phosphite to1,2-dibromoethane 3.0:1.0, the mass of the catalyst 0.5% of reactant. The yield under this optimum reaction conditions was up to 90•9%. ESI-MS、IR and1HNMR were used to characterize its chemical structure. Its reaction conditions were discussed.