Abstract: The construction of metro station underneath or parallel to pile foundation of the bridge causes large area excavation unloading at the side of bridge pile foundation. The operation safety of existing bridges will be threatened due to lateral friction resistance decrease caused by metro construction adjacent to friction pile. A calculation formula of lateral friction resistance friction pile foundation adjacent to metro station is deduced by simplifying the force on existing friction pile foundation as four parts and it is verified in the construction of North Taipingqiao Station of Beijing metro line 19. The results show the maximum lateral friction resistance loss ratio is 42.8% when the excavation depth of metro station is larger than the length of pile foundation; the excavation width of metro station has a little influence on lateral friction resistance loss; injection reinforcement of the soil mass around the pile foundation before construction can enlarge the internal friction angle with the proper range of 25°-30°.