With the acceleration of the urbanization and industrialization of China, it is inevitable that cultivated land converts to built-up land for industrial, commercial and residential uses, which would impose pressure both on food security and on the sustainability of urbanization itself for such a country with large population and fcw cultivated land. Based on the three-time Landsat Thematic Mapper (TM) digital images and statistic data of Hcbei Province, the general facts of cultivated land conversion and its driving forees were analyzed by establishing econometric model in this paper. Some conclusions were drawn as the following: during 1985-2000, the rate of cultivated land converting to built-up area in Hebei was 4.01% or 0 27% per year Of all the converted cultivated land, 20.96% was converted to built-up area and of all the new built-up arcas, 83.4% was converted from cultivated land; meanwhile the conversion is uneven not only in time but also in space; factors such as edge length shared by cultivated land and built-up land, agricultural value per hectare, non-agriculture value per hectare, GDP, total population, farmers net income per capita and time had significant effccts on this conversion.