Tunnel under the Xi’an Subway Line crosses the main bridge pile of Xianyang International Airport, and thus active underpinning pile foundation treatment has to be used.Based on the combination of design engineering, we made underpinning beam (Beam-Pier-cap-pile connector) 1∶6 overall model，selected connecting surface of the joint type form of chiseling + drill anchorage + interface gel + prestressed,and underpinned the structure of the force performance and reliability of the analysis and demonstration.The results show that underpinning beam strength and stiffness can meet the requirements, the limit load of the specimen on its corresponding original underpinning girder is up to 9 900 t, and underpinning beam has a high load carrying capacity, ductility of the specimen is good and safe.Deformation coordination is under the upper large axial force bridge load,and the connection of chiseling + drill anchorage + interface gel + prestressed has the desired effect.