Abstract: The unclassified tailings slurry is emitted with low mass concentration in Beiminghe iron mine.However, it is generally difficult to meet the concentration requirements of tailings consolidation piles in the surface subsidence areas through the method of natural settlement.Therefore, the unclassified tailings slurry needs to be further flocculated and concentrated by adding flocculants.In this study, the unclassified tailings slurry with a mass concentration of 38% and nine types of flocculants are chosen as experimental materials, and the static flocculation and sedimentation tests are conducted to investigate the effect of flocculants types and dosages on the flocculation and sedimentation property of the unclassified tailings slurry.Moreover, the optimal flocculant types and its dosage are determined by analyzing the settlement time, sedimentation velocity, and mass concentration of slurry after settlement.The experimental results show that compared with the slurry by natural settlement, adding the concentration of 1‰ flocculants solution have promoting effect on the sedimentation velocity of the unclassified tailings slurry, and the anionic polyacrylamide flocculant (APAM) with a molecular weight 12 million has the best flocculation effect.And its corresponding optimal flocculant unit consumption is 40 g/t, which can increase the unclassified tailings slurry from 38% to the required concentration of 46% in the shortest time.This can meet the requirements of the flocculation and sedimentation concentration of the tailings consolidation and piling in the surface subsidence areas.