Based on land use data of Wuxi City in 2005,the GIS technology and the Minimum Cumulative Resistance Model（MCR model）are applied to analyze the spatial potential developing trends of the sources ofarchipelago type and network type and identify positional critical portion.Results are as follows:（1）InWuxi City,the critical portions of sources connecting type are arranged in three parts with amount of 23patches.The area of invasion in Yixing part is the biggest;Jiangyin part,in the middle;and Binhu part,thesmallest.The destroyed degree of invasion in Jiangyin part is the worst;Binhu part,in the middle;and Yixing part,the least.（2）The critical portions of network controlled type are arranged in two parts with amount of 40patches.From both views of area of invasionand destroyed degree of invasion,Biyi part are bigger or worse thanJiangyin part.（3）The positional critical portions are in amount of 56patches,which can be classified as twogroups and eight sub-groups.Among these portions,the portions with key importance are in amount of 13patches and the portions with common sense are in amount of 43patches.The spatial arrangement of positional critical portions has a close relationship with that of physical geographic traits of studied area.