The paper mainly discusses the sequence of casual factors which impacts upon human errors. According to hierarchical framework of human error causal factors, relativity analysis method in grey systems theory, human factor events in certain organization and Root Cause Analysis, the results by quantitative calculation are obtained as following: the order of main factors causing human error is organizational factor, personal factor, technical factor and environmental factor. The most important one among various sub-factors contributing to human errors is managerial control factor, and the second ...