The invention relates to a rectangular large section steel structure assembled temporary support pipe joint jack-in mechanism. Pipe-jacking construction is an underground pipeline construction method, a surface layer does not need excavating, but under the restriction of geological conditions and the section size, the pipe-jacking construction is not generally applied. The rectangular large section steel structure assembled temporary support pipe joint jack-in mechanism comprises a working well and a receiving well, a pipe-jacking section is arranged between the working well and the receiving well, and the pipe-jacking section is formed by a plurality of steel pipe joints. Each steel pipe joint is assembled by steel plates in a splicing mode, and the overall section of each steel pipe joint is in a rectangular shape. The surfaces of outer pipes of the steel pipe joints are face plates, and longitudinal rib plates perpendicular to the face plates and parallel to the direction of channels are arranged on the inner surfaces of the face plates. Transverse rib plates which are perpendicular to the longitudinal rib plates and parallel to the cross sections of the channels are arranged between the longitudinal rib plates. An end plate is arranged at the position of one pipe end face of each steel pipe joint. H-section steel is arranged in inner pipes of the steel pipe joints in a transverse and vertical intersection mode. The jack-in mechanism can effectively reduce self-weight and jacking force of a pipe-jacking structure, overcomes the defect that a pipe-jacking heading machine can not be used, and achieves the application of large section steel pipe joint jack-in method process in shallow buried subway auxiliary projects.