In order to research the deformation effect of the whole process of underpass construction on the adjacent existing subway tunnels, the Dongming Road pedestrian and non-motorized underpass project of Jinshui Road (West 3rd Ring Road to East 4th Ring Road) project in Zhengzhou City is taken as the background, and the finite element software Midas GTS is used to establish a three-dimensional numerical model, and analyze the influence of pipe jacking and foundation pit construction on the deformation of the existing subway tunnels, the horizontal displacement and settlement change characteristics of the adjacent existing subway tunnel during the construction process of the new underpass is summarized, and the values are compared and simulated with the engineering monitoring data to verify the reliability of the numerical model. The results show that the maximum horizontal displacement and vertical displacement of the tunnel of Metro Line 1 induced during the whole process of the construction of the underpass tunnel are 0.52 mm and 2.12 mm respectively, and the maximum horizontal displacement and the vertical displacement of the existing subway tunnels meet the control standards. The results can provide references for the design, construction and monitoring of similar engineering.