Measuring system for measuring displacement and extension value of bending point before and after bending and rebounding measuring tube

The invention discloses a measuring system for measuring displacement and an extension value of a bending point before and after bending and rebounding a measuring tube. The measuring system comprises an arc-shaped graduated disk 99 arranged at a circular-disk-shaped embryonic membrane bending pipe of a pipe bending machine and a changerable type tail-section slide scale base 3 which is fixed to an embryonic membrane, wherein a tail-section slide scale 4 with ruler scales in the radial direction of the embryonic membrane is arranged in a slide base of the changerable type tail-section slide scale base 3; a first digital display module 98 which is fixedly arranged relative to the changerable type tail-section slide scale base 3 and adopts an electronic reading mode is arranged on the tail-section slide scale 4; the outer end of the tail-section slide scale 4 is fixed to a second digital display module 97 through a pin roll; the second digital display module is arranged on a front-section slide scale 2 with rul