The title compound N,N’,di(diethoxythiophosphoryl),1,4,phenyl,enediamine was synthesized by the reaction of diethoxythiophosphoryl chloride with p,phe,nylenediamine and characterized by elemental analysis,IR, and 1H NMR spectra. Its crystal structure was determined by X,ray diffraction analysis and the thermal property was studied by TG analysis. The relative molecular weight of the title compound is 412.42. The crystal structure belongs to the orthorhombic, Pbca space group, with a=0.86936(16) nm, b=1.2787(2)nm,c=1.8897(3)nm,β=90°, V=2.1006(7) nm3, Z=8, Dc=1.304 g/cm3,μ(Mo Kα) = 0.425 mm,1, F(000)=872, S=1.052, the final R=0.0628 and wR=0.1860 for 1852 observed reflections with I＞2σ(I). The X,ray diffraction analysis demonstrates that the crystal structure is centrosymmetric.observed to link the molecules into sheets. The TG analysis shows that the title compound has good thermal stability and char forming capability and its fire retardation for polyacrylonitrile reveals that the compound is an excellent intumescent fire retardant.