Abstract: A systematic research on the knowledge base building in the expert system of spectrometric oil analysis(SOA)and fault diagnosis is carried out theoretically as well as practically. The knowledge building is the core of an expert system. A comparative research about the theory and method of knowledge building is carried out. Through the investigation, knowledge collect and scene test, fuzzy logic and fuzzy cluster methods are adopted in explaining the data from different aspects. Good accuracy and applicability can be improved by combining these useful methods and expert knowledge. The method of knowledge establishing specially suitable for the condition is summarized.

Key words: air cr aft engine, SOA, exper t system, knowledge base