Abstract: Effective additives are required for polymeric materials used in a variety of applications to endow them with flame retardancy.Organosphosphorus flame retardants are often very effective but the effectiveness always depends on the structure, content of phosphorus and thermal stability of phosphorus-containing compounds.Consequently, two novel arylene bisdi(pentaerythritol phosphate) phosphate flame retardants were synthesized using pentaerythritol, phosphorus oxychloride, resorcinol and bisphenol A materials, and their structures were characterized by elemental analysis, ¹H NMR, and Fourier transform infrared(FT-IR) spectroscopy.An investigation on their thermal properties shows that the resorcinol bisdi(pentaerythritol phosphate) phosphate flame retardant with 5 wt % of mass loss is about 350℃ and residue at 600℃ is as high as 57.6%, which shows that the novel flame retardant possesses of thermal stability and charring property.