Radar remote sensing can detect micro relief, building, vegetation distribution, surface roughness and water content sensitively. It is a very useful means for these studies. Based on Radarsat Scan SAR data supplied by Center of Canadian Remote Sensing (CCRS), the pattern of spatial structure of urban system dominated by physical geographical factors is studied in Huang-Huai-Hai plain. Physical geographic condition is foundation for urban forming and developing. A case studies patterns of spatial structure of urban system in different physical geographic factors (i.e. river, paleo channel, and landform) in Huang-Huai-Hai plain. The results are listed as follows: (1) In peneplain with plenty water resource, hexagonal spatial structure of urban system can be formed. Due to differential competed function of central places, the hexagonal system is distorted. The result is that the area covered is decreased and the girth is unchanged——but every border is usually unequal; (2) A pattern of pentagonal system evolves from hexagonal system controlled by a river; (3) A pattern of quadrilateral develops from hexagonal system under two parallel rivers; (4) The equal distance distribution of central places in narrow geographic space has its special reasons. The results are very important for understanding urban’s formation and development and urban plan in Huang-Huai-Hai plain.