By analyzing the causes of frequent cracks in the web of bridge box girders, it is shown that the existing anchorage system of fine-rolled rebar has the defect of excessive retraction, and a feasible anchorage system that can effectively solve the problem of excessive retraction is put forward - strand vertical prestressing anchorage system, and the tensioning process and equipment are improved, so that the tensioning is easy to operate and reliable. The operation is convenient and reliable. The strand vertical prestressing anchorage system can ensure the designed prestressing in the box girder web, and can effectively improve the durability of the box girder web.