In order to improve the flame retardancy of the poplar, CS/h BN/APP thin films with good flame retardant properties are successfully prepared on the wood surface through electrostatic adsorption between the positively charged chitosan/hexagonal boron nitride(CS/h BN) polyelectrolyte solution and the negatively charged ammonium polyphosphate(APP) solution based on the layer by layer self assembly(LBL)technology. The characterizations of scanning electron microscope(SEM) and energy dispersive spectrum(EDS) indicate that CS/h BN/APP coatings have equably spread over the surface of wood. Coating adhesion test indicates that the coating has excellent adhesion performance. Cone calorimeter tests show that heat release rate(HRR) and smoke production rate(SPR) of assembled wood samples are all significantly reduced, the second peak heat release rate(Pk HRR) and peak smoke production rate(Pk SPR) appear later than that of the untreated woods. During the combustion, residual mass of the assembled wood samples is always higher than that of the untreated woods and the time to burn out is about 100s more than that of untreated woods, and the effect is gradually enhanced with the increase of the number of self assembly layers. The production of CO and CO2gas of the assembled wood samples are significantly reduced, indicating the flame retardant coating can effectively reduce wood smoke and toxic gases release. The char residue indicates that the assembled wood samples preserve the structure of the wood better than that of the untreated woods, showing a good fire resistance.