Abstract: Tailing slurry of coal preparation plants features fine size of particles and a high content of fine clay. How to make effective settlement of it is a long-standing problem that still remains unsolved. In order to seek a better way for its settlement, the tailing slurry from the coal cleaning plants under Xinwen Mining Group is taken as the object to explore the effects on settling of the slurry produced by use of flocculant alone and by combined use of coagulant and flocculant. As indicated by study results, with the use of flocculant alone, the settling velocity is lower than the combined use of coagulant and flocculant. Based on results of experimental study on the effects that can be obtained by using the two agents in combination, the regime of agents in the case of using both agents is further optimized using response surface method. Study result shows that, in terms of significance, the effects of dosage of coagulant on initial settling velocity and turbidity of supernatant are greater than the effects produced by the time interval between dosing of the two agents; with the increase of dosage of coagulant, the initial settling velocity of tailing slurry tends to first increase and then decrease while the turbidity of supernatant shows a tendency which is just the opposite of that of settling velocity; after optimization with response surface method, it is noted that within the experimental range, effective settling of the slurry can be expected under the optimal conditions of a time interval of 60 s, a coagulant dosage of 72.16 g/t and a flocculant dosage of 99.9 g/t; under the above-mentioned optimal settling conditions, the model-predicted settling velocity and supernatant turbidity values are 65.03 cm/min and 11.52 NTU, respectively, well indicating the high accuracy of the model and its capacity for optimization of settling effect; and fractal dimension analysis shows that the use of ammonium salt coagulant KD-1 and flocculant APAM in combination can lead to increase of number of fractal dimensions and structural compactness of flocs.