Abstract: Carrying out county ecological risk assessment can provide a scientific basis for county ecological risk prevention and ecological environment protection. Taking Tang County, Hebei Province as the research area, based on the land use data of 2000, 2007, and 2018, this paper constructed an ecological risk evaluation model from three aspects of risk source, risk receptor exposure, and risk effect, and analyzed the ecological risk, time-space changes, and influencing factors before and after the transformation of unused land in Tang county. The results showed that from 2000 to 2018, the area of unused land providing ecological space decreased significantly, the area of grassland and woodland provided ecological space, the area of cultivated land provided production space, and the area of towns and residential areas provided significantly increased living space. The change of land use type made ecological space transform into living space and production space. After the transformation of unused land, the ecological risk of the study area increased slightly from 0.079 in 2000 to 0.107 in 2018, the proportion of low-risk areas decreased, and the proportion of medium and high-risk areas increased, which was at a low-risk level. The indicators related to ecological risk were land use index, construction land proportion, farmland non-point source pressure, and population pressure. We should reasonably plan and develop unused land, pay attention to ecological control from the source of risk, and strengthen ecological construction. The results are significant for future land use and management and maintaining ecological balance.