The invention discloses an U-shaped beam bridge erection machine with a rail distance change self-adaption function. The U-shaped beam bridge erection machine comprises a front support leg cross beam, a middle support leg cross beam and a back support cross beam; two main beams are arranged on the front support leg cross beam, the middle support leg cross beam and the back support cross beam; a longitudinal movement system is arranged on the two main beams, and comprises two longitudinal movement cross beams; the two ends of each of the longitudinal movement cross beams are arranged on the two main beams through traveling wheel frames; a transverse movement trolley is arranged on the longitudinal movement transverse beams; a lifting device is arranged on the transverse movement trolley; sliding shoe type support legs are arranged at the parts, near the two ends, of the front support leg cross beam, the middle support leg cross beam and the back support cross beam; a sliding device is arranged between each sliding shoe type support leg and the corresponding support leg cross beam. The U-shaped beam bridge erection machine has the advantages that the distance change of double-line U-shaped beam can be automatically adapted, the U-shaped beam can be continuously erected between a main line and an island type station, the additional occupation of social roads is not needed, the additional set of erection equipment and method is not needed, and the integrated benefits of the beam erection are greatly improved.