The invention relates to a construction method of an assembled rail transit elevated bridge and a structure and belongs to the technical field of rail transit building. The method comprises steps of (1) prefabricating U-shaped beams, a cover beam, a pile column and pile foundations, (2) hoisting the pile foundations on-site and casting a bearing bench on the tops of the pile foundations, and orderly arranging the pile column and the cover beam from bottom to top, (3) installing bearers and a contact net, and (4) arranging the U-shaped beams on two sides of the contact net, and fixedly connecting the bottoms of the U-shaped beams with the upper ends of the bearers. With prefabricated components and an on-site assembling construction method, component quality can be guaranteed and on-site land occupation can be reduced, and construction time can be reduced.