Abstract: Locomotion interference will happen when wheel pipe-robot passes through bent pipes or irregular pipes.In order to solve this problem,tri-axial differential wheels are incorporated into the drive system of pipe-robot,which will make the wheel pipe-robot adapt to the pipe environment automatically.The mechanical structure of the mechanical self-adaptive pipe-robot is designed and studied.Meanwhile,kinematical simulation and analysis have been made on the the 3dimensional model of the pipe-robot,and it is validated that the pipe-robot with tri-axial differential wheels can accommodate the bent pipes better and have better stability in the pipe.Strong self-adaptability,compact structure,high drive efficiency,reliability and low cost are the characteristics of the robot.