To explore the characteristics of the support structure for a folding hydraulic lifting dam during operation, combined with a practical project, the stress change laws after reinforcement under different opening angles were analyzed by FEM. Also, the effects of sediment deposition height in front of the dam on the support structure were analyzed. The results show that under the pressure of actual overflow head which led to the destruction of hydraulic lifting dam, the maximum value of the principal stress in the folding strut first increases and then decreases with the increase of opening angle. The most dangerous working angle is 45°. As the opening angle increases, the maximum value of the principal stress in the support seat first decreases, then increases, and decreases at last. Its most dangerous working angle is 0°. At the opening angle of 45°, the average tensile stress in the anchor bolt reaches the peak of 59. 46 MPa. At the opening angle of 0°, the average shear stress in the anchor bolt reaches the peak of 75. 56 MPa. The average stress is lower than that before reinforcement, indicating that the support structure is safe and feasible. The sediment deposition before the dam mainly has an adverse effect on the stability of the folding support structure.