Abstract: A study is specifically made of the effect on settling of coal slurry produced by the following factors: comprehensive flow field environmental factors, dosages of flocculant and coagulant, type of flow field, flow field energy input and acting time of agents, so as to define the optimum coal slurry settling conditions. Test result shows that: the most prominent influential factor is the type of flow field, followed by energy input, dosage of agent, and acting time of agent, in terms of degree of influence; the type of flow field and flow field energy input are the most crucial factors; compared with the radial, axial and mixed flow fields, the latter is most beneficial to the settling of coal slurry through flocculation; and a relatively good slurry sedimentation result can be obtained with the radial-flow impeller running at a speed of 400 r/min.