In order to fill the subsidence area with total tailings in some iron mine,a process of cementation slurry preparation by hydrocyclone-thickener classifying and thickening experiments was introduced,and the industrial experiments of preparation process was carried out.The experimental results showed that the high-efficient thickening of total tailings and the preparation of cementation total tailings slurry with thickness more than 60% and good rhelogical property can be achieved using the classifying-thickening process.The process has the characteristics of simple flow,high condensing efficiency,low investment,small workshop area and low productive cost,and it is convenient to be industrialized for the mine.