The ecological security pattern is of great significance for ensuring regional ecological security, promoting high-quality development of urban space, and enhance human welfare. This paper focuses on the basic naturally geographical features and ecological environment issues of the karst mountain areas,and explores the construction and optimization of the ecological security pattern in the ecologically fragile karst mountain areas. Taking the city of Hechi as an example, we identified and selected ecological sources according to the importance of ecosystem services, modified the basic resistance surface based on the results of ecological and environmental sensitivity assessment, and extracted the ecological corridor with the Minimum Cumulative Resistance model (MCR model) to construct the ecological security pattern of Hechi The results show that the total area of ecological source area in Hechi is 5706.63 km², accounting for 17.07% of the city's total area. The ecological corridor is divided into potential corridor and key corridor, which are 456.82 km and 325.44 km, respectively. The overall planning of the identified source areas and ecological corridors can form a spider web pattern of ecological security of radiation distribution of "four screens, two areas and three belts". Based on the identification of the importance of ecosystem service function and the method of modifying the basic resistance surface by using the results of ecological sensitivity, the importance of ecological process in the construction of ecological security pattern is taken into consideration. The results provide the practical path and scientific guidance for solving the problems of urban space expansion and ecological security in karst mountain areas.