The influence of excavation of newly built loess tunnel in plateau area in Taiyuan, Shanxi on stability of existing adjacent tunnel is analyzed by empirical evalution method and 3D numerical simulation method. The analytical results show that: 1)The influence of loess tunnel excavation on deformation of existing tunnel increases with the distance between two tunnels decreasing when the newly built tunnel is located in the limit domain of the existing tunnel. 2) The influence of loess tunnel excavation on middle of axial line of the existing tunnel is the biggest when then newly built tunnel is located in the attention domain of the existing tunnel.