The invention discloses a step-length-fixed telescopic automatic walking mechanism, belongs to the technical field of automatic walking and particularly relates to a step-length-fixed telescopic automatic walking technology used for detecting the inner wall of a pipeline. The step-length-fixed telescopic automatic walking mechanism is composed of a front shell and a rear shell, wherein the front shell and the rear shell are respectively provided with an elastic supporting structure and a
locking mechanism. The front shell and the rear shell are connected together through a
threaded rod motor, a threaded sleeve and a guide pillar. In the process of advancing, the
locking mechanism of the front shell is unlocked, the
locking mechanism of the rear shell is locked, the
threaded rod motor rotates to drive the front shell to advance partially by a regulated distance, then the locking mechanism of the front shell is locked, the locking mechanism of the rear shell is unlocked, the
threaded rod motor rotates to drive the rear shell to advance partially, and in this way a
walking cycle is finished. The maintaining performance and interchangeability are good, automatic walking can be performed well, the
walking distance is high in uniformity each time, the
automation degree is high, positioning precision is high, and reliability is high. Meanwhile, time, efforts and labor are saved, and it is guaranteed that the surface quality of the inner wall of the photoelectric instrument detection pipeline is accurate and comprehensive.