In order to explore the situation of water resources carrying capacity in Nanjing, this paper selected 14 indicators to establish the evaluation index system of water resources carrying capacity,and compared and evaluated the level of water resources carrying capacity in Nanjing from 2003 to 2012 by using the principal component analysis.The results show that population and economic development, water resources endowment and utilization efficiency of resources are the main factors affecting the capacity in Nanjing;the water resources carrying capacity in Nanjing from 2003 to 2012 was on the positive tendency apart from 2004．On the whole，the development trend of carrying capacity in Nanjing is good but still exists certain rising space.