Abstract: The construction of underground subway stations often has to underpass the existing building structures. However, there is less relevant construction experience underneath the existing tunnel bridges. As smooth traffic needs to be ensured in the existing tunnel bridges, it is very important to ensure the safety of tunnel bridges and quickly restore traffic while constructing subway stations.Taking the construction of Harbin Metro Line 3 Haping Road Station underpassing the Tunnel Bridge of Health Road as an example, the underpinning reinforcement construction technique of the underpass above the station passage was introduced in detail. To examine the reliability of the construction technology, the whole process of the construction of the passage underpassing through the existing tunnel bridge was numerically stimulated to analyze the deformation settlement of the underpinning reinforced tunnel bridge during the excavation construction at the lower station.The analysis results showed that the maximum vertical deformation of the underpinning reinforced tunnel bridge was only 2.35 mm. The maximum stress was 0.210 MPa, which was much smaller than its tensile deformation and strength design value. This proved the reliability of the underpinning reinforcement scheme adopted for the tunnel bridge.