The stretching-bending straightening unit (referred to as "stretch straightening machine") is a new straightening equipment developed to meet the high requirements of the flatness of the strip, which integrates the advantages of the roller straightening machine and the stretching-straightening machine. Its working characteristics are that the strip produces plastic extension under the joint action of the tension roll stretching and the bending roll continuous alternating and repeated bending. It can eliminate the three dimensional shape defects of the strip, such as ladle bend, edge wave shape and sickle bend, and obviously improve the shape quality.