Territorial spatial evaluation and zoning management play a pivotal role in territorial spatial planning, which serves as a vital tool for facilitating coordinated regional development. This study focuses on 88 county units in Guizhou Province to establish a comprehensive functional zoning evaluation index system for national land space. The system integrates six aspects of national land space functions: agricultural production, industrial development, human settlement services, tourism services, mineral resource supply, and ecological services. Subsequently, the functional zoning of national land space in Guizhou Province was optimized and adjusted based on this evaluation. The findings reveal several key insights. First, there is significant variability in the evaluation of individual functions of Guizhou Province's land space, with industrial development and tourism and leisure functions comprising the highest proportions at 30.68%. Second, driven by social and economic development, some counties and regions have undergone functional transformations, transitioning from primary agricultural production areas to key development zones. Third, except for three counties primarily focused on ecological service functions, all other counties and regions exhibit multi-cluster and multi-functional development patterns. This study provides decision support for the rational development and utilization of national land space in the karst mountains of Guizhou Province. Furthermore, the methodological approach and findings of this study serve as a valuable reference for the functional zoning and optimization of national land space.