A fuzzy expert system for defect inspection of TFT-LCD is proposed. Because the defects of TFT-LCD are of strong complexity and vagueness, it is very difficult to establish accurate mathematical models for the defects. Combining expert system with fuzzy set theory,the defect inspection system could make good use of expert experience and knowledge to solve the problem of vagueness and uncertainty which is existed in the process of defect inspection without complex mathematical models. The results show that the rates of both miss and false detection are lower than 3 % and can meet the expected requirement.