The article evaluates the ecological security of land for five cities in Southern Jiangsu Province by matter-element model to present the trends of the ecological security and the regional differences of their influencing factors.The results show that:(1)The main factors promoting the ecological security of the land are economic factors while the negative factors vary from regions to regions:the use of pesticides brings great threats to Wuxi,Changzhou,Suzhou and Zhenjiang City;the industrial waste gas decreases the ecological security in Nanjing City;the industrial waste water has negative effects on Suzhou and Wuxi City and the high population density brings different threats to all five cites.(2)Uenerally,the ecological security of the land in the five cities were improved to higher levels from 2003 to 2009 either steadily or rapidly,and there is much chance and space for the situation in Nanjing,Changzhou and Zhenjiang City to be improved.