The filtration of kaolinite-coal mixture suspension was investigated by settling behavior observation and filter cake structure analysis. Three-dimensional X-ray microanalysis was used to analyze filter cake structure. The settling rate and specific filter cake resistance of kaolinite-coal mixture gradually increased with the increasing content of kaolinite in suspension. A high settling rate made filter cake form quickly during filtration, which prevented water to pass through, increasing the specific filter cake resistance. Filter cake structure analysis showed kaolinite trapped fine coal particles into the gap between kaolinite flocs during filtration. The size and number of pores in the filter cake formed by a high kaolinite content mixture were smaller and fewer than that formed by a low kaolinite content mixture. A high specific cake resistance was created by a high kaolinite content mixture. This study provides a novel insight into the filtration of coal slurry in coal mining and cleaning processes. (C) 2020 Elsevier B.V. All rights reserved.