Abstract: The sketch network,which is often used in water resource system to simplify the studied problems,is seldom used for system analysis.In fact,knowledge related to the sketch network could be used to analysis the system deeply,which is common used in social system and communication system.In this paper, the concepts of the node-weighted core degree and the node-weighted core are introduced into water resource system.According to experts' knowledge,we can weight the elements of the system,that is,the nodes of the sketch network,and then measure the importance of elements of system from the sides of function and structure.Therefore,the core engineering of system can be founded.Based on these concepts,the hierarchical structure of system is studied,and an algorithm calculating the hierarchical structure is given here.