The urban ecosystem is a social-economic-natural comprehensive system.the meaning of its carrying capacity is different from that of the resource and environment capacity.Scholars at home and abroad have studied the academic and practical aspects of ecosystem capacity and have acquired numerous research results.At present,the foci of the study are changing from the natural ecosystem to the complicated man-made ecosystem.In this paper,the theory of carrying capacity is reviewed and extended to the urban ecosystem.Based on the study of the urban ecosystem carrying capacity and the relationship between each subsystem,we built the quantitative model to evaluate the extent to which the urban ecosystem carrying capacity has reached from.The indexes of the model include carrying index,consisting of resource supply capacity(RS),environmental carrying capacity(EC),ecosystem reliance capacity(ER) and social-economic envelopment(SE) and pressure index which is consist of resource expenditure(RE) and surrounding pollution(SP).A case study in Wujiang city is described.Building the index system and employing the evaluation model,the complex carrying capacity of Wujiang city during 1990-2004 was evaluated.The result indicated that relationship between the ecosystem carrying capacity and the development of socio-economic system evolved from unbalanced to relatively balanced.Among each selected indicators,the average percentage of environmental carrying capacity(EC) index reached 38.68%.This indicator is the important factor which enhances the urban ecosystem carrying capacity and restrains the growth of the ecosystem pressure.The average percentage of resource expenditure(RE) index reached 54.45%,indicating that resource expenditure resulted from of socio-economic development is still the main cause of the ecosystem pressure.