On-line real-time detection method for the defect of TFT-LCD is becoming increasingly important as TFT-LCD has replaced CRT displays and become the first choice in many applications. Traditional defect inspection methods of TFT-LCD are based on clear features and exact mathematic models. However, the defects of TFT-LCD are of strong complexity and vagueness. Moreover, determining the defects is a complicated process, which is influenced by the objective characteristics of the defects as well as the subjective factors of the observer. Therefore, it is very difficult to establish the accurate mathematical models for the defects. A fuzzy expert system approach is proposed for the defect inspection of TFT-LCD. Tests indicate that this system could emulate the experts or experienced operators to realize the automatization of the defect inspectin of TFT-LCD.