Abstract: In this paper, a new in pipe mobile carrier mechanism is presented on the basis of wheel type and crawler type in pipe mobile mechanism. It uses two motors to drive two sets of six wheels at the front and the rear respectively. The wheels are distributed symmetrically on the robot body and are pushed against the inside wall of pipe by spring force. Viewd from circumferential direction, the wheels are distributed on three sets of parallelograms, combining the wheel type and crawler type in pipe mobile mechanism skillfully. Therefore the robot mechanism has a very good capability to traverse barriers. This robotic mobile carrier has high efficiency, and can work reliably. Its structure is particularly suitable to the inside pipe wall where concave barriers exist.