The invention relates to an assembly lifting appliance of a vertical beam and a horizontal beam under an arc of a midheight deck steel pipe concrete arch bridge, which comprises a horizontal beam lifting appliance and a vertical beam bracket. The assembly lifting appliance is characterized in that: the horizontal beam lifting appliance comprises two symmetrical extended steel plates, a screw rod vertically passing through one end of the two symmetrical extended steel plates, and bolt group holes arranged at the other end; and the vertical beam bracket comprises a bracket main body, and two parallel joist steel carrying poles, wherein the bracket main body consists of two groups of parallel Berea beams which are mutually and fixedly connected by profile steel, and the two parallel joist steel carrying poles are vertically connected with the upper sides of both ends of the two groups of parallel Berea beams. The invention also relates to an assembly method of the vertical beam and the horizontal beam under the arc of the midheight deck steel pipe concrete arch bridge. The assembly lifting appliance and the assembly method have the advantages of achieving a cable rope system of a non-shift system to lift the horizontal beam under the arc, shortening assembly time of the vertical beam and conveniently and rapidly completing jointing, positioning of the horizontal beam and the vertical beam, ensuring the safety of operators by a bracket platform and greatly saving project cost.