Abstract: In this research, some core cities in the Yangtze RiverEconomic Beltwereselected as the case study, such as  Wuhan, Shanghai and Chongqing. Firstly, the PSR model was  used to build up the framework ofthe index systemof ecologicalsecurity evaluation with the characteristics of the area in the Yangtze RiverEconomic Belt., which consisted of  target, criterion and indexlayers, including totally31 indicators. Then the principal componentanalysis method was adopted to determine  the weight of the index, so as to reduce the influence among the indexes and makethe weights of the indicators moreobjective.Finally, the gray clustering model based on the whitening weight function wasconstructed to assess ecological securitystatus of the three cities from 2004 to 2015.The results show that the level of ecological security the three citieshas been increasedfrom 2004 to 2015, and the ecological security status has been improved.