Abstract: Visual fatigue of X-ray machine operators is investigated in order to understand the intensity of their workload,and provide a reliable method for a comprehensive,objective and synthetic evaluation of fatigue level.Based on a complex system of human-machine-environment-management,features of visual fatigue resulting from search processes are analyzed.According to its characteristics,3 first-level indices are established,including visual fatigue,mental fatigue, and local muscle fatigue.Then 1 9 second-level indices are also designed.A model based on fuzzy synthetic evaluation of second-level indices is developed to comprehensively evaluate visual fatigue of X-ray machine operators.Analytic hierarchy process (AHP)is used to determine the weight of first-level and second-level indices in this evaluation.Data for evaluation matrices in this model is collected through 100 valid questionnaires.Using this fuzzy distribution method,evaluation re-sults of second-level indices are:the high or severe fatigue ratio of operators in vision system,neural system,and local muscle is 54.9%,50.2% and 49%,respectively.The corresponding results of first-level indices are 63% of the X-ray ma-chine operators,indicating a high or severe state of fatigue.According to the principle of maximum membership degree, the maximum degree of membership of first-level indices is 0.44,and the X-ray machine operators of this airport are in a state of high fatigue overall.