The shrinkage and creep loss of concrete, the elastic-plastic compression loss of concrete, the relaxation loss of steel tendon, the friction loss of vertical prestressed reinforcement and the loss value of anchorage are calculated. The field measurement and analysis of vertical prestress loss are completed. The calculation and measurement results after compared show that the calculation methods are effective, applicative and safe to calculate the loss of vertical prestressed reinforcement of box girder, which have the technical reference value for the similar engineering calculation applications.