This paper, according to some relevant literatures, the actual production of mining and the reason analysis of mine casualty accidents recently, makes analysis on overfull ratio, the level of mining technology, funds inputted on safety technology and the quality of the employees, and nine ingredients affecting the mine casualty are determined. Combing the accident statistics of one mine in Shandong province, the grey system theory is used to make relational analysis on these nine ingredients which indicates that operation against rules (OAR), command against rules (CAR) and the overfull ratio (TOR) are the main effect ingredients leading to mine deaths, that OAR, CAR and mechanization degree of mining are the main effect ingredients resulting to severe or minor wound accidents. The superiority analysis and sensitivity analysis all reveal that OAR is the most sensitive ingredient leading to coal casualty accidents. This method is simple and of higher precision, offering a new thought and way to assess accurately the key ingredients leading to coal casualty accidents and prevent them.