Abstract: In order to effect efficient treatment of high mud-laden coal slurry, orthogonal test is made on the effects of kaolinite, quartz and montmorillonite on settlement and clarification of high mud-laden coal slurry, with an aim to bring to light the law governing the effect and mechanism of the respective mineral composition as mentioned above. Test result indicates that kaolinite exerts the principal effect followed by montmorillonite with quartz coming last. The 3 kinds of clay minerals tend to become size degradation in water and form micro-size particles, rendering the slurry very difficult to treat because of the presence of their strong surface electronegativity and interparticle hydration repulsive force. The effect of each clay mineral on the treatment of mud-laden coal slurry varies, depending on its surface potential, function group and swelling property in water.