Defects such as insufficient forming, instability and wrinkling seriously emerge in the pushbending for thinwalled and small bending radius (R=1D) elbow with long straight tube. The pushbending of thinwalled and small bending radius (R=1D)elbow with long straight tube was studied by changing friction coefficient and forming internal pressure. The results show that the internal pressure of tube has a significant influence on the forming of elbow, the instability wrinkling in the bending section of tube emerges because of too small pressure, and  the defects such as insufficient forming and head fracture of elbow are prone to occur due to large pressure.Moreover, the friction between the outer wall of tube and the mold cavity also has an important influence on the forming of elbow, and the material flow of tube along the axial direction is hindered and the length of elbow is reduced due to excessive friction. In the experiment, polyurethane filler and supramoly were respectively used as elastic medium and lubricant, and the thinwalled and small bending radius elbow with long straight tube were formed by pushbending with internal bulging. And the thickness reduction of its outer wall is controlled within the scope of security.