The invention provides a system and a method coupling activated carbon pyrolysis gas preparation and biomass direct combustion denitration. The system comprises: a carbonization furnace for performinga carbonization reaction on a raw material and generating initial pyrolysis gas; a secondary combustion chamber used for receiving the initial pyrolysis gas generated by the carbonization furnace through a first pipeline for combustion, one part of the combusted pyrolysis gas being introduced into the carbonization furnace through a second pipeline for heat exchange, and the other part of the combusted pyrolysis gas being introduced into a biomass incinerator; and the biomass incinerator used for receiving the combusted pyrolysis gas generated by the secondary combustion chamber and the pyrolysis gas subjected to heat exchange in the carbonization furnace so as to carry out a denitration reaction. According to the system and the method, the pyrolysis gas generated in an activated carbon preparation carbonization process is introduced into the biomass incinerator, and reacts with nitrogen oxides generated by biomass incineration, so that the purpose of removing nitrogen oxides is achieved, and meanwhile, the pyrolysis gas prepared from the activated carbon can be efficiently and cleanly utilized.