Abstract: The deep cone thickener plays an important role in the field of mine tailings treatment and resource recovery，but the change of tailings particle size has a significant effect on its operation perfor‐ mance. Taking Baoshan Mine in Hunan Province as the research object，the whole tailings were mixed in different proportions，and the particle size distribution，rheology and dynamic flocculation sedimentation tests were carried out，and the numerical simulation was carried out. The test results show that the particle size composition，rheological parameters and sedimentation performance of different graded tailings are ob‐ viously different，and the particle size of tailings affects the sedimentation speed and concentration effect. Based on the paste filling theory，in order to deal with the change of tailings particle size，the countermea‐ sures of optimizing process parameters（adjusting feeding speed，flocculant addition amount and rake frame speed）and tailings pretreatment（classification and grinding）are put forward to improve the opera‐ tion efficiency of deep cone thickener and provide technical support for the sustainable development of min‐ ing enterprises.

Key words: deep cone thickener, tailings size, settling performance, thickening effect, optimization countermeasures