Work system safety is a function of many factors, besides it is dynamic and complex. There may be relations and dependencies among the safety factors. Therefore, work system safety should be analyzed in a holistic manner. In this study, the accidents data analysis is used to identify the links among the factors; the relationship analysis of the independence between the behavioral factors has been performed in order to find the non-independent factors. Among the Human Factors Analysis and Classification System (HFACS), the impact of the high-level factors on the bottom level is determined. After a period of monitoring and rectification, it implements a new round of safety monitoring and factors comparison and interaction analysis, so to achieve the goal of “the nature of safety” of hydropower projects construction.