Abstract: It is more complex and difficult to perform structure analysis for the spanning part of Cangzhou-Linyi oil pipeline under the unsymmetrical loading when the slippage effect of inclined flexible steel cable induced by the movement of the pulley in bearing tower top. Differential equations were obtained according to the geometrical and deformation relationship about cable slippage, stretching and pipeline transverse displacement, which would be useful to calculate balancing tension force and then analyze the cause on the rupture of under-stretching steel. The numerical simulation calculation has been made, the future influence on the safe operation to the pipeline has also been estimated due to the greater transverse deformation on the spanning part after the rupture. The results show that the method outlined by the authors in the paper is available.