Abstract: The expansion behavior of thin-walled circular tube was studied by the finite element method and the existing expansion experiments. It was found that the geometric dimensioning <i<h</i< and <i<D</i<<sub<1</sub< of the expanded tube were mainly affected by the initial geometric parameters of the tube and die, but less affected by the metallic materials and friction coefficient. According to the dimensional analysis, the dimensionless relationships between the geometrical dimensioning (<i<h</i<, <i<D</i<<sub<1</sub<) and the main influencing factors were obtained. Then, based on the above dimensionless relationships and the law of conservation of energy, a new prediction model of the steady compression force was put forward, in which the effects of strain hardening and die diameter on the curvature of the bending regions of expanded tube were also taken into account, and the predictions of the current model are in good agreement with experiment and simulation data.