Abstract: The geological conditions of Dianchi Basin are complex, and soluble rocks are distributed in many parts of the basin and the edge of the basin. The Karst problem is prominent and has a great influence on metro. The investigation of Karst in metro needs to be carried out through multiple stages using comprehensive survey technology to find out its characteristics, properties and hazards. After investigation and analysis, the Karst weak development of the Dahegeng Station of Kunming metro Line 4~Datangzi Station Section, Chenggong East Station(including)~Kunming South Railway Station Section, Liandajie Station~Chenggong East Station Section, Bailongtan parking lot and the Karst middle development of the entrance and exit section line, The Karst section of Jindingshan Station~Xiaocaiyuan Station developed strongly. Line 4 is covered Karst. Karst mainly develops in the 15m range below the base rock surface, and is dominated by filled caves with a height of 0.5~3.0m. The average hole rate of boreholes is 21%, and the average line Karst rate is 3.29%.The Karst area is divided into stable area, sub-unstable area and unstable area. Karst management should adopt corresponding treatment principles and engineering measures for different engineering types and Karst characteristics. Karst treatment generally adopts grouting reinforcement measures. For Karst with a small buried depth, excavation to expose backfill grouting can be used for reinforcement treatment. The pile foundation needs to pass through the Karst and be placed in the lower stable strata. This paper has some guidance for the Karst survey and treatment of metro in Kunming.