The invention relates to the technical field of shock absorption control in civil engineering of pedestrian bridges, in particular to a semi-rigid support device used for a pedestrian bridge. The device comprises a lower connecting steel plate connected with a pier. The lower connecting steel plate is provided with a steel plate guardrail. Two rows of horizontally-placed spring supports are arranged in the steel plate guardrail. Each spring support comprises an upper steel plate and a lower steel plate which are connected through multiple screws. Each screw is provided with a spring. The two ends of each spring are correspondingly arranged in fixing blocks. The two ends of each lower steel plate are correspondingly installed in clamping grooves through lower bolts. The two ends of each clamping groove are welded to the lower connecting steel plate through supports. The upper steel plates are connected with the girder end of the bridge through upper bolts. By the adoption of the semi-rigid support device, the adjustability of the rigidity of the supports is achieved, so that the natural frequency of vibration of the plates is changed and is away from the natural frequency of vibration of pedestrians as far as possible, semi-rigid connection of the bridge and the pier can be achieved, the purpose that the frequency of the structure can be adjusted is achieved, and therefore the bridge meets the requirement for the vibration comfort level.