Abstract: In order to explore the law governing the separation of coal and kaolinite in coal slurry water in flotation process, test on flotation of coal and kaolinite in a separate and artificially mixed manner and the test on contact angle of coal and kaolinite is conducted so as to analyze the effect of concentration of collector n-dodecane on flotation characteristics of coal and kaolinite as well as the separation characteristics of the two minerals at different mixing ratios. Test result shows that: in the case of making separate flotation of coal and kaolinite using n-dodecane at a dosage of 800 g/t, a widest difference in recovery rate can be observed between the two, with the former being 92.12% and the latter 42.34%; for flotation of coal and kaolinite in a mixed manner at varying mixing ratios, a fairly good separation result can be expected with a separation efficiency all greater than 75% which can go up to 80.23% at a mixing ratio of 1∶1; and it is noted from the variation of contact angles, in comparison with kaolinite, coal exhibits a higher n-dodecane adsorptivity.