An air preheating and denitration integrated reactor and reaction method. The reactor includes a rotary catalyst body, housing arranged outside the rotary catalyst body, and gas inlet and outlet channels on upper and lower surfaces of the housing; the gas inlet and outlet channel is in divided three, namely flue gas, reductant, and air inlet and outlet channels, the rotary catalyst body is cylindrical and includes a central shaft rotor and multiple circular catalyst layers rotate around the central shaft rotor, each circular catalyst layer is divided into air, flue gas and reductant zones by a radial sealing plate and axial sealing plate. In each circular catalyst layer, a catalyst in the reactor alternately circulates in flue gas, reductant and air zones. The catalyst performs heating-reheating-cooling process on catalyst layers along with the reactor rotation, different temperatures and reaction atmospheres in zones conductive of air preheating and denitration.