Abstract: Objective: Reasonable reinforcement and excavation of paralle overspanning upper foundation pit are key to ensuring foundation pit stability and controlling existing underlying tunnel displacement. Construction scheme for foundation pit excavation should be reasonably selected for effectively controlling existing tunnel deformation and ensuring foundation pit safety and stability throughout construction. Method: Based on the foundation pit engineering practical case of Gangxia North Hub South Area in Shenzhen, finite element numerical simulation method is used to simulate the construction process, the impact of different foundation pit excavation schemes under different dewatering depths and reinforcement range conditions on the deformation law of the existing underlying tunnel is analyzed. According to the analysis of the underlying tunnel deformation control effect, the construction plans were compared and selected，and a reasonable construction scheme is selected and finally verified by fieldmeasured data. Result & Conclusion: Research results show that excavation of the longdistance parallel overspanning upper foundation pit is prone to cause a large vertical displacement of the existing underlying tunnel; the fieldmonitored results are in good agreement with the corresponding numerical simulation results, and the recommended scheme of dewatering to tunnel bottom and strip reinforcement below the pit bottom can effectively control the displacement of the existing underlying tunnel.