Size-adjustable pile foundation reinforcement cage inner supporting device

The utility model relates to the field of bridge engineering pile foundation construction, and discloses a size-adjustable pile foundation reinforcement cage inner supporting device, which comprises three adjustable supporting rods, a plurality of supporting rods and a plurality of supporting rods, wherein the adjustable supporting rods are length-adjustable rod bodies and are triangularly and horizontally arranged in a reinforcement cage; the three connecting units are arranged at the vertexes of the triangle defined by the adjustable supporting rods and internally tangent to the circular transverse reinforcing ribs in the pile foundation reinforcement cage in a transverse moving mode. A construction method of supporting rib welding in traditional pile foundation construction is replaced, the reinforcement cage can be detached and reused after being machined, the problem of waste of the inner supporting ribs is solved, 100% recycling of the inner supporting ribs is effectively achieved, resources are saved,