The invention discloses a temporary structure for installation of a continuous steel girder bridge and a beam segment construction method thereof. The structure comprises a pylon and a displacement adjusting device, the pylon comprises a pylon main beam, a pylon beam, a pylon main beam stiffening plate, a pylon main beam ear, a bridge top surface ear and a pin shaft, the pin shaft is connected between the pylon main beam ear and the bridge top surface ear, and the displacement adjusting device comprises a vertical jack, a horizontal jack, a counter-force seat, a limit groove and a bridge top surface steel plate. The method comprises the steps of a, the design of the temporary structure; b, the production of a rack; c, the production of the displacement adjusting device; d, the continuous construction of the beam segment. The structure has the advantages of small consumables, simple installation and disassembly, cost saving and short construction period, is not limited by the line typeof the main beam of the bridge, and can well control the positioning accuracy of the main beam of the pylon; the steel beams are not limited by construction conditions during segmentation, and a segmentation line is set at the zero bending moment according to the force condition, thereby reducing the internal stress of the position weld of the segmentation line and indirectly increasing the connection strength of the two sections of the steel beams.