Abstract: Lignin-based intumescent flame retardant(Lig-T) with carbon source, acid source and gas source was synthesized successfully by grafting nitrogen and phosphorus elements. The structure of the flame retardant Lig-T was proved by Fourier transform infrared spectrometer(FT-IR), elements analysis and X-ray photoelectron spectroscopy(XPS). The Lig-T was added to the epoxy resin with different mass fractions to obtain Lig-T/EP composite material. Thermogravimetric analysis, underwriters laboratories 94(UL-94) vertical buring test, oxygen index(LOI) test and cone calorimetry(Cone) test were used to investigate the thermal stability and flame retardancy of composite materials. The results showed that when the mass fraction of the Lig-T was 20%, the composite material 20% Lig-T/EP could reach the UL-94 V-0 level, the oxygen index value was as high as 28.5%, and the mass fraction of the residue increased from 14.8% to 20.2%.With the increase of the mass fraction of Lig-T, the total amount of heat release and the total amount of smoke released during the combustion process of the composite material decreased.