The invention belongs to the field of grid structure buildings, and particularly relates to an aluminum alloy connecting piece of a building grid structure and a processing method of the aluminum alloy connecting piece. The aluminum alloy connecting piece comprises a sleeve, a sealing plate, a high-strength bolt and an aluminum alloy pipe, wherein the sleeve, the sealing plate, the high-strength bolt and the aluminum alloy pipe are sequentially arranged from left to right, the sleeve and the sealing plate are sequentially arranged on the high-strength bolt in a sleeving way, and the sleeve is fixedly arranged on the high-strength bolt through a tightening bolt which is arranged on the outer circumferential surface of the sleeve; the outer circumferential surface of the sealing plate is provided with a plurality of circles of convex edges, the sealing plate is fixedly arranged at one end of the aluminum alloy pipe in a pressing way, and the convex edges are embedded into the inner wall of the aluminum alloy pipe when the sealing plate is pressed. According to the aluminum alloy connecting piece and the processing method, disclosed by the invention, the technical problems in the prior art that the specific gravity of a steel member is large, the steel member is easily rusted, the welding of the aluminum alloy connecting piece is difficult, and the like are solved.