Abstract: This paper presents an intelligent computer-aided design method,which is the combination of the expert system technique and the modelling and optimization technique l for the urban water supply network improvement.In the paper, the design procedure of the network and the functions of two kind of techniques in the procedure are analysed first.Then,the knowledge type and the method of knowledge acquisition for the network layout with the expert system technique are developed.Furthermore, a mathematical model of the parameter optimization for the network and water resources is constructed,and a decomposition algorithm to solve it is also proposed.The simulation results show that the design method is advanced and effective.