Fire safety of interior wooden structures is closely associated with the flammability of indoor wooden structures. The effect of the treatment with phosphoric nitrogen boric(P N B) components based fire retardant FRW on the dynamic combustion behaviors of the plywood was investigated using a CONE calorimeter at a heat fluxes of 25, 50 and 75kW/m2 respectively. The results show that the peak value of heat release rate(pkHRR), quantity of smoke release, and fire growth index(FGI) of untreated plywood are quite high, suggesting a high fire risk. The treatment of plywood with a P N B components based fire retardant FRW results in a greater char yield and less release of heat and smoke compared to those of untreated controls; Increasing fire intensity during test only slightly influenced the yield of carbon monoxide. Consequently, it demonstrates that the treatment with P N B components based fire retardant FRW can significantly restrain the combustion and reduce the yield of heat and smoke.