Abstract: In order to study the collapse mechanism of a mine tailings dam andcomprehensive treatment, the following aspects are investigated:the granularity composition and strengthparameters of mine tailings, the distribution of tailings deposits, the change of seepage condition of the dam bodydue to the rainfall and flood impounding of the tailings reservoir and drainage facilities.The stability against sliding of the dam is analyzed. According tounsaturated soil theory, the main reasons causing dam collapse includethe increasein water content of soil resulting from rainfall and flood impounding and the decrease in shear strength due to the decrease of soilsuction, as well as the insufficient drainage and reinforcement.Some comprehensive treatments for partial collapse of the dam are alsosuggested.