Urbanization is a necessary tendency of mankind progress in 20 century , urban system is the regional combining form of urbanization , whose occurrence and development have the necessary and close connection with the surrounding natural system , and this connection is adequately shown by the regional features , the spatial pattern and ( the spatial ) arranging rules of urban system 城市化是二十世纪人类发展的重大趋势之一，城镇体系是城市化发展的地域组合形式，其发生、发展与周围的自然系统存在着必然的、紧密的联系，这种联系充分体现在城镇体系的地域特征、空间格局与布局规律上。
