The invention discloses an overbreak shovel blade for a rectangular pipe jacking machine. The overbreak shovel blade comprises a blade holder and a blade. The blade is mounted on the blade holder, isin the shape of a triangular pyramid and comprises a top surface, two side surfaces and a cut-in edge, a first alloy blade is arranged on the top of the blade, second alloy blades are arranged on thetwo side surface, and a third alloy blade is mounted at the cut-in edge; the blade holder comprises a front surface and a back surface, a limit pin is arranged on the back surface of the blade holder,the front surface of the blade holder comprises a front pressure surface and an oblique pressure surface, fourth alloy blades are arranged on the front pressure surface, fifth alloy blades are arranged on the oblique pressure surface, and a sixth alloy blade is arranged at the front end of the oblique pressure surface. The overbreak shovel blade has the advantages that the overbreak shovel bladeis provided with the blade in the shape of the triangular pyramid and accordingly can be quickly cut in soil mass; the overbreak shovel blade is provided with six types of alloy blades, accordingly, overbreak can be carried out on blind zones, bonding of residual soil can be reduced, and the construction efficiency can be improved; the overbreak shovel blade is reasonable in structure and convenient to mount.