The method of using expert system and fuzzy theory in fault diagnosis for substation is brought out in this paper by comparing power system fault diagnosis methods and principles in our country and foreign countries . we study mainly the expert system whose knowledge base has many features and advantages and bring out the method of dealing with the uncertaingtity by fuzzy theory <中文摘要> =本文通過比較國內(nèi)外電力系統(tǒng)故障診斷方法和故障判斷原則,提出了將專家系統(tǒng)和模糊理論用于變電站故障診斷的方法? ?主要以研究專家系統(tǒng)為主;對用模糊推理來處理不確定信息進(jìn)行了初步的探討。