The invention relates to the technical field of bridge construction and concretely relates to a repairing method for a U-shaped rib inner side weld joint. A defect weld joint is repaired from the external side of the U-shaped rib; a to-be-repaired joint is exposed from and between the lower end of a U-shaped rib side plate and a base plate; the U-shaped inner side corresponding to the to-be-repaired joint is provided with a lining pad preventing welding rod melt water flowing into the inner side of the U-shaped rib; the joint is welded on the external side of the U-shaped rib; and after the weld joint is stabilized, the lining pad is taken out and weld joint repair work is completed. The weld joint repairing technology is simple and convenient to operate; internal weld joint repairing efficiency can be improved and weld joint repairing difficulty can be lowered; and great promotion value can be provided.