Timely and accurately obtained regional construction land information for environmental protection, ecological construction, and regional planning is important. In this study, we used Landsat7 ETM+ images acquired in 2002 and Landsat8 images acquired in 2016 as data sources, and performed maximum likelihood classification and class masking in order to extract construction land information in Tongren. The experimental results showed that the construction land of the study area was 306.07 km² in 2002 and 675.15 km² in 2016. This shows an increase of 369.08 km², which marks an increase by 120.59%, while the expansion ratio was quite larger. Construction land was mainly transferred from cultivated land (338.65 km²), and shows that large areas of cultivated land were replaced by construction land. The main reason for the construction land increase was urban expansion, and the county expansion ratio was between 3.72 and 7.92. Road construction, mining destruction, and residential expansion are additional reasons, but these have caused smaller changes to the area of construction land, with a change ratio of only 0.34. In mountainous Karst areas, urban expansion may cause ecological problems; therefore, we should protect the natural environment and maintain the landscape in its original state so as not to cause excessive disturbance to land resources.