Based on the collection and analysis of regional geological data, preliminary investigation results, previous research results and similar engineering cases, the main hydrogeological and engineering geological problems should be found out in the fine survey of karst platform high-pressure water rich super long tunnel. Hydrogeological and engineering geological mapping and geophysical exploration should be carried out to solve these problems, and the geological model should be constructed on this basis. The methods of hydrogeological drilling, engineering geological drilling, field monitoring and testing and numerical simulation are used to verify, enrich and optimize the geological model. Taking Yuanguping tunnel of Zhangjiajie to Guanzhuang section of G59 Hubei expressway as the research object, in order to find out the hydrogeological and engineering geological conditions of high-pressure water rich super long tunnel in karst platform, this paper explores and studies the fine survey in the aspects of hydrogeological and engineering geological mapping, geophysical exploration, geological drilling and engineering evaluation, and puts forward the technical ideas of fine survey. According to the idea of fine survey technology, the groundwater system in the tunnel area is subdivided into 17 groundwater systems, and the tunnel passes through 9 groundwater systems. The hydrogeological structure of Dahu Village section is investigated by using the air DTH hammer borehole and TV composite method. On this basis, the tunnel water inflow is predicted by using analytical method and numerical method. The tunnel water inflow is 26.93×10⁴ m³/d. The risk of water and mud inrush is evaluated. The karst spring system in Dahu village and the karst underground river system in Baiyangping are high risk areas.