Abstract: In order to prevent water accidents, according to the accidents causation theory "2-4" model and using the statistical theory, taking the coalmine water accidents occurring during 2000 to 2009 as the research objects, we analyze the unsafe acts in the water accidents of 68 coal mines, and classify those unsafe acts and count the frequency. The research results show that the obtained 413 unsafe acts can be classified into two categories as well as six subcategories. Among the two categories, proportion of violation and non-violation is respectively 99.5%, 0.5%; among the six subcategories, proportion of violation command and non-command is 32%, 14% respectively, proportion of violation operation and non-operation is 21%, 31% respectively, and proportion of violation movement and non-violation is 2% together. The conclusions show that the primary job of controlling violation is to reduce the high frequency unsafe acts in commanding and operating by means of training, and a new method for classifying the unsafe acts is proposed.