Abstract: In order to solve the problems of locomotion interference and decline of traction force,reduce the abrasion of transmission parts caused by the environment restriction when the roller pipeline robot getting across the elbow,a drive tech-nology of roller pipeline robot with a mechanical adaptability named as tri-axial differential drive is studied.The mechanics principle of differential velocity of tri-axial mechanism is expatiated through the mechanics analysis.The traveling-capability of the tri-axial differential pipeline robot when getting across the elbow are validated through the theoretical studies on dif-ferential property and traction force of the robot.