Yangji StationWuyangcun Station on No.5 Line of Guangzhou Metro goes underneath through Dongshan District, where there are many buildings and heavy traffic. Due to the need of pile foundation underpinning of Guojielou building, how to guarantee zero influence on the traffics during underpinning construction becomes a topic of top priority. Based on the study and analysis of ground situation, the design theory of underpinning in tunnel is proposed. Calculation analysis of feasibility and structure of underpinning in tunnel, analysis of influence of negative friction generated by underpinning construction in tunnel on the pile foundations, and calculation analysis of force bearing of pile and beam underpinning model show that underpinning in tunnel is practical. Then, the author presents the key in the design and construction of underpinning in tunnel. The use of underpinning in tunnel guarantees the construction schedule and quality of the project.