Abstract: This paper analyzed the topographic and geological characteristics, deformation process and trend, landslide causes, stability, treatment plan, and monitoring data of the Zhengjiayuan tunnel-landslide oblique system. In addition, a comprehensive treatment plan was given, which could be described as unloading the landslide mass, ramming and grouting cracks, setting up anti-sliding piles and anchor-cable anti-sliding piles on the left and right sides of the tunnel crossing the sliding surface respectively, canceling the short subgrade before the tunnel to connect the bridge and tunnel, intercepting and draining away water in the surface and internal part of the landslide, and reinforcing local landslide protection. The tunnel-landslide oblique system is a typical three-dimensional structure. When the tunnel body is closer to the sliding surface, the stability of the landslide will be worse, and the damage caused by the landslide to the tunnel will be more serious. In terms of the influence of spatial location relationship on landslide stability, the traverse on the sliding surface is larger than that on the sliding bed. When the overlying soil layer of the tunnel-landslide oblique system is thick, and the sliding surface is steep, the vertical deformation of the tunnel is greater than the horizontal deformation. When the overlying soil layer is thin, and the sliding surface is gentle, the horizontal deformation is greater than the vertical deformation. When the tunnel passes through the landslide mass, especially the sliding surface, weak blasting and short footage construction should be adopted, and the support parameters should be strengthened. The time consumed by each construction process should be shortened, and the quick closure of the tunnel lining should be emphasized. Furthermore, the monitoring and measurement should be improved and encrypted. Zhengjiayuan tunnel-landslide has undergone heavy rains, and it is generally stable and shows a positive control effect. Therefore, it is necessary to combine automatic monitoring and manual inspection to complement each other and give full play to their advantages, so as to jointly ensure the safety of structures.