Along with the development of “Industrial 4.0”, the application of industrial robot is becoming more and more extensive. Based on the industrial robot platform, a novel robot tube bending technology has been proposed. In order to provide guidance for the forming quality of tube bent by robot, using the plastic forming theory and simulation analysis method, compared with the rotary draw bending, the forming mechanism and characteristics of robot tube bending were analyzed. The Al6061 thin-walled tube with small diameter was taken as the research object. The results show that, in the novel robot tube bending process, since the bending die is feeding in the direction of the pipe axis while rotating, it will reduce to some extent the axial tensile stress T on the pipe during the bending process. Therefore, compared with the traditional rotary draw bending, the tensile stress and strain and thinning rate on the outer side of bent tube are both smaller, while the compressive stress and strain and thickening rate of the inner tube are instead larger in the robot tube bending process. With the increase of bending angle, the maximum cross-sectional distortion of bent tube in the robot tube bending process remains basically unchanged and is always smaller than that in the rotary draw bending process, and the greater the bending angle, the more obvious the difference. In summary, the robot tube bending technology plays a more positive role in reducing the thickness reduction and section distortion of the small diameter tube.