Urban boundary and area is an important indicator for urban sprawl analysis. However, concept and extraction standard of urban boundary were inconsistent, and the resolution of images was coarse, resulting in lower precision and incomparable urban boundary. To solve above problems, a semi-automatic method of urban boundary extraction is proposed by using high-resolution image and geographic information data. Urban landscape and form characteristics, geographical knowledge, and a series of standardized rules are combined to generate high-precision and consistent urban boundary. Urban boundaries of China's 337 prefectural cities in year 2000, 2005, 2010 and 2016 are extracted with above-mentioned method. Together with other thematic data, urban sprawl is analyzed. Results show that: ① China's prefectural cities has undergone a rapid urbanization from year 2000 to 2015 with a high degree of concentration and regional differences. ②The efficiency of urban land use is significantly related to the development level of urbanization. The sprawl models of most cities are extensive. ③Most cities are faced with the problem that urban expansion is ahead of population growth, while a few cities expansion lag behind population growth. ④Cultivated land is the main source of urban expansion areas.