The invention provides a large-scale portal frame. The large-scale portal frame comprises two rails, two trolleys, two stand columns, a movable main beam and a connection beam. Two ends of the movable main beam are respectively erected on the stand columns and are connected to a lifting device. Upper ends of the two stand columns are connected by the connection beam. The large-scale portal frame also comprises at least two counterweight mechanisms, a connection beam adjustment mechanism and two suspention beams for fixing manipulators. The counterweight mechanism comprises a guide wheel group, a suspension cable and a counterweight block. The connection beam adjustment mechanism comprises at least one adjusting nut, at least one adjusting screw and an adjusting seat. The two suspention beams are symmetrically fixed to the movable main beam, one end of each one of the suspention beams is close to the center of the movable main beam and any one of the suspention beams is provided with a horizontal movement mechanism. The manipulators are connected to the suspention beams by the horizontal movement mechanisms. The large-scale portal frame satisfies span and height requirements and is suitable for 3D printing building extruding head arrangement.