Abstract: Ecological pressure and ecological elasticity are the two important forces affecting ecosystems.Based on the interactions of the two,an index system was established for evaluation of ecological carrying capacity and with the Yangtze River Delta being a case for study,ecological carrying capacity of the complex system was evaluated.Results show that though the ecological pressure index of the region,including Shanghai City,Jiangsu Province and Zhejiang Province,somewhat fluctuated,on the whole it rose gradually in the past ten years and its ecological elasticity demonstrated basically a rising trend and its ecological carrying capacity did an improving trend as well.Nevertheless,the region is still under high pressure,and even in a state of ecological imbalance.

Key words: ecological carrying capacity, complex ecosystem, evaluation, the Yangtze River Delta