The utility model discloses a noise and emission reduction exhaust pipe for an APU (auxiliary power unit). The noise and emission reduction exhaust pipe comprises a main pipeline part, a resistive noise elimination ring cavity, and an exhaust gas transformation ring cavity, wherein the diameter of a middle segment of the main pipeline part is larger than that of a front segment and that of a rear segment of the main pipeline part to form the resistive noise elimination ring cavity, the resistive noise elimination ring cavity is fixed circumferentially on the outer side wall of the middle segment, is internally filled with a porous acoustic material and is communicated with the interior of the middle segment, and the exhaust gas transformation ring cavity is fixed circumferentially on the outer side wall of the rear segment, is internally filled with a catalyst and communicated with the interior of the rear segment. The exhaust pipe provided by the utility model can effectively reduce noises as well as harmful gases like CO, HC and NOx. The exhaust pipe provided by the utility model is convenient to install and does not affect the auxiliary power unit or other parts of an airplane.