This paper discusses current concept of water resources carrying capacity.Furthermore,different definitions are compared and relations among these conceptions are analyzed in this study.It is suggested that the definition should consider abundant practicability besides on ecology,environment and sustainable development.Meanwhile "reasonable development scale" is applied to describe the conception of water resources carrying capacity.Based on the definition,the influences of water saving operations are analyzed,and a new calculation system of water resources carrying capacity is suggested to employ advanced evolution algorithms.This paper uses the model to carry out the research into water resources in the Liaohe River Basin,and the results show that the model is efficient.