Abstract: In this paper,various factors which involve international market oil price are analyzed.Then,by using design methodology of large scale expert system,concrete design of oil price forecast expert system is given.In it,new knowledge representation methods are used.In the system structure,model base,way base,knowledge base and data base are used.Flexible multi-level reasoning machine and intelligent interface are adopted.The system is realized in Turbo-Prolog language on PC/AT computer.Operation results show that the new design methods are very effective and they supply experience for designing othere conomic expert systems.