The invention provides a taper sleeve adaptive type outer support for 20-roller large tension rolling. The taper sleeve adaptive type outer support comprises a swing oil cylinder, a bracket and a swing door, wherein the swing oil cylinder is fixedly mounted on the bracket through a base arranged on the bracket, a piston rod of the swing oil cylinder is hinged to a support arranged on the swing door, the swing door is positioned in the middle of the bracket, and the swing door and the bracket are in rotating connection through hinge pins; a cylinder body is arranged on the swing door, a cylinder cover is mounted on the inner side of the cylinder body, the piston rod is mounted in the cylinder body, a sliding column is arranged on the swing door, and the sliding column is connected with the piston rod through a screw; the other end of the swing door is connected with a locking rod, the other end of the locking rod is connected with the piston rod locking the oil cylinder, and the locking rod penetrates through a sliding sleeve mounted in a fixed base so as to control the opening and locking of the swing door. The taper sleeve adaptive type outer support is high in rigidity and great in stability, and the taper sleeve has the advantages of being rapidly adjustable and adaptive and can adapt to the rolling work conditions of large tension and high roll weight.