A novel intumescent flame retardant (IFR) 5,5-dimethyl-2-phospha-1,3-dioxan-2-yl acrylamide methoxy phosphate was synthesized with neopentyl glycol, phosphorus oxychloride and N-hydroxymethyl acrylamide, using triethylamine as acid acceptor and CuCl as catalyst. The structure of the compound was characterized by elemental analysis, FTIR and 1H NMR. The yield of the compound was 75.3% with the molar ratio of N-hydroxymethyl acrylamide to triethylamine being 1:1, the mass fraction of CuCl being 1.5% N-hydroxymethyl acrylamide, and the reaction in ice-water bath for 2 h at first and then in room temperature for10 h. And the thermal properties of the compound were tested by TG and DSC techniques. The TG curves of the compound indicates that the initial thermal decomposition temperature is about 210℃, and there is about 40% char residue left at 800℃, indicating that the title compound has a good thermal stability and a char forming capability.