Provided is a concrete box-girder bridge girder web plate structure.Anchoring blocks vertically corresponding and arranged along the bridge direction at intervals are added to two outer side faces of a girder web plate, and external vertical prestressed steel bars composed of finish-rolled threaded steel bars are installed on the vertically corresponding anchoring blocks.During construction, the external vertical prestressed steel bars are tensioned in the mode of screwing nuts at the lower ends of the external vertical prestressed steel bars, meanwhile the 1-order vibrating angular frequency during tensioning of the external vertical prestressed steel bars is measured through vibration pickup devices installed on the external vertical prestressed steel bars, tensile forces produced inside the external vertical prestressed steel bars are calculated according to a formula, and the tensioning of the external vertical prestressed steel bars is stopped when the tensile forces reach theoretical tensile forces produced inside the external vertical prestressed steel bars.The effect of preventing the web plate from producing cracks is played by adopting the method for forming a vertical pressure stress on the girder web plate through the external vertical prestressed steel bars, and meanwhile it is ensured that an original bridge structure is not damaged by too large tensile forces.