Remotely sensed images and historical aerial photographs at seven different periods are used to study urban expansion in Yixing city, in the Taihu Lake region, East China in the last 50 years. The results show that the urban area of Yixing expanded by more than 8 times, and the annual expanding rate was only 3% before 1984, and 21% from 1984~2000. Within each period more than 90% of the expanded area is cropland. The expansion was characterized differently from period to period. Before 1984 the urban area expanded separately along the old city boundary, after that the city began to expand along main roads and highways, and then filled in the empty blocks between the roads. The urban development is also confined by river systems, which is a representative characteristics of urban expansion in the Taihu Lake region in China.