The utility model discloses an external prestressing force reinforcing structure of pier bent cap, including twice lay respectively waiting to consolidate the bent cap around the external prestressing steel of both sides restraint, two lay respectively and carry out the anchored anchor waiting the atress support and two sets of the restrainting respectively of consolidating the bent cap left and right sides to the external prestressing steel of twice, external prestressing steel restraints along horizontal bridge to laying, two sets of anchors are the symmetry to be laid, and every group anchor includes all that it carries out anchored prestressed anchorage utensil to restraint both ends to external prestressing steel respectively for two, and two prestressed anchorage utensils are located two atress support outsides respectively, atress support clamp is adorned in the prestressed anchorage utensil and is waited to consolidate between bent cap left side wall or the right side wall, the atress support includes by the many shaped steel supports that are shaped steel that the level laid and constitute. The utility model has the advantages of simple structure and reasonable design and simple and convenient, the excellent in use effect of construction can solve higher, the relatively poor scheduling problem of reinforcement effect of reinforcement method complicacy, input cost that current bent cap reinforcement method exists.