A novel reactive flame retardant based on L-cysteines containing P, N and S flame retardant elements was synthesized, and using its good water solubility, different concentrations of flame retardant poplar wood powder were prepared, and using the hot pressing process method, flame retardant density boards were made and their flame retardancy was studied. The thermogravimetric infrared coupler (TG-FTIR) test and thermal cracking gas mass spectrometer (Py-GC–MS) test both revealed that the flame retardant modified the thermal decomposition pathw...