Dibromoneopentyl glycol chlorophosphate (II) was prepared by reaction of neopentyl glycol and phospous oxychloride. Then novel free-flame retardant neopentyl glycol dipyrophosphate (III) was synthesized by the hydrolysis reaction of compound II. The over yield was 72% and its structure was identified and studied by elemental analysis, IR, ¹H NMR, MS techniques and X-ray diffraction analysis. The crystal belongs to orthorhombic, space group pbca with unit cell dimensions a＝0.97690(2) nm, b＝1.1283(2) nm, c＝2.6506(5) nm, α＝90(3)°, β＝90(3)°, γ＝90(3)°, V＝2.9217(10) nm³, Z＝38, D_c＝1.429 g/cm³, μ＝0.322 mm^－1 and F(000)＝1328. The final R＝0.0507 and R_w＝0.1254 for 3327 unique reflections [I＞2σ(I)]. The result of thermal analysis shows that the novel flame retardant has a high thermal stability and excellent char forming ability.

Key words: flame retardant, synthesis, crystal structure, thermal decomposition