A scientific definition of the type of mountain area and an exploration of the spatial correlation between different types of mountain areas and regional land use at the county level are important for reasonable land resource utilization and regional sustainable development. Here, a geographic information system was used to analyze digital elevation model data and to define the extent of mountainous land and types of mountain areas in Guizhou province. Exploratory spatial data analysis was used to study the spatial coupling relation between the type of mountain area and land use degree in Guizhou province at the county level. The results were as follows: (1) Guizhou province has a high proportion of mountainous land, with a ratio of mountainous land to non-mountainous land of 88:11. The county-level administrative units in Guizhou province were exclusively mountainous, consisting of eight semi mountainous counties, nine quasi mountainous counties, 35 apparently mountainous counties, 13 type I completely mountainous counties, and 23 type II completely mountainous counties; (2) The land use degree at the county level in Guizhou province have remarkable spatial differentiation characteristics. Counties with a high cultivation coefficient are mainly located in the western area along the line between Yinjiang county and Anlong county in west Guizhou province. Counties with a large proportion of construction land or a high integrated index of land use degree are mainly distributed in the economically developed area of central Guizhou province, including parts of the counties (districts/cities) administrated by Guiyang, Zunyi, Liupanshui, Anshun, Duyun, and Kaili; (3) County-level administrative units with relatively flat topography and a low proportion of mountainous land have a large proportion of construction land and a large degree of regional land exploitation. However, the extent of cultivation of county-level administrative units under similar topography differs considerably; (4) The increase in urban land intensity and the decrease in cultivated land intensity are distinctive features of land system change in mountain areas, which is conducive to the sustainable development of mountain.