Under the special geological structure of the Tibetan Plateau, karst development is unique in the region. To explore the development characteristics and investigation method of plateau karst and to provide a reference for tunnel route selection in plateau karst areas, a case study is conducted on a tunnel project in southeast Tibet. The investigation reveals that various levels of planation surface topography, geomorphology, and structural characteristics are present. The periodical development characteristics of karst in the plateau are analyzed according to corresponding paleoclimate characteristics. Moreover, using the survey data of surface karst phenomena, airborne electromagnetic physical exploration, and deep hole drilling results, the vertical zoning law of karst is further analyzed. The feasibility of analyzing the development degree of plateautype karst based on the evolution of planation surface is verified. Further, the distribution of water points in the tunnel area is statistically analyzed. The characteristics of filling diameter and discharge of karst water are analyzed using the flow rate and isotope test results and the karst development law. The vertical zoning of karst groundwater is divided. Finally, the potential risks of tunnel engineering in the karst area are analyzed. The estimation formula of tunnel route selection and engineeringsetting countermeasures are proposed to reduce the risk of karst collapse and strong water gushing in tunnel construction.