The invention discloses a mechanism for bending a petroleum pipeline. The mechanism comprises a winding shaft, a jumping-prevention board, a supporting assembly and a pipeline clamping part; the jumping-prevention board is located on the top of the pipeline clamping part, a through groove is formed in the jumping-prevention board, and the projection of the through hole on the top face of the pipeline clamping part is in an arc shape; a sliding block is arranged on the pipeline clamping part, and is located in the through groove, the supporting assembly comprises a mounting plate, a supporting rod, a cross beam and a lower pressing rod which are sequentially connected, the axis of the cross beam is perpendicular to the axis of the supporting rod, the axis of the lower pressing rod is parallel to the axis of the supporting rod, and the end, away from the cross beam, of the lower pressing rod is connected with the end face, away from the pipeline clamping part, of the jumping-prevention plate. The jumping-prevention plate limits jumping of the pipeline clamping part along the axis of the winding shaft, appearing of the condition that the pipeline moves towards the axis of the winding shaft during bending can be avoided, radial shearing force of jumping generated by power transmission on the bending portion is removed in the pipe bending process, and the quality of the bending portion is improved.