Changes in the geostress field are recognized as one of the important factors that induce deformation and failure of oil and gas pipelines. Hence, the pipeline routing with considering geostress field change can better guarantee pipeline safety. However, due to the complex topographic relief conditions in mountainous areas, its geostress field is usually changeable and it is often difficult to obtain geostress field in mountainous areas. The present pipeline routing in mountainous areas nearly does not include the factor of geostress field change. In order to better support the routing of oil and gas pipelines in mountainous areas and maintain pipeline safety, the distribution of shallow-surface geostress fields in mountainous areas was obtained through numerical modeling in this study, and a path planning algorithm was applied to evaluate the routing of oil and gas pipelines in such regions. This study has further refined the consideration dimensions for oil and gas pipeline route selection in mountainous areas. The results show that the geostress field in shallow surface areas is significantly impacted by topographic relief. At locations with higher elevation, such as at mountain ridges, compressional stresses are lower, and at these locations, even tensile stresses can occur. On the contrary, at locations with lower elevation, such as at valleys, compressional stresses are higher, and stress concentrations can often exist here. All paths obtained by the path planning algorithm detour the more dangerous areas, effectively avoiding the pipeline safety problems that may be caused by the geostress field change. Results of the study offer valuable insights and references to improve the comprehensiveness and completeness of pipeline route selection of oil and gas pipelines in mountainous areas.