Abstract: The coal-flotation test of low-rank coal was carried out.by taking the low-rank coal of a coal preparation plant in Mahuangliang, Inner Mongolia as the research object, using the gravity-purifying coal from a coking coal preparation plant in Shanxi as the carrier material. The industrial analysis and XRD test of low-rank coal are carried out firstly. The results show that the coal samples have high volatile content, and clay minerals in the coal samples mainly contain kaolinite and montmorillonite. Then the low-rank coal flotation test with different particle size carriers and carrier recovery test were performed. The results show that the carrier with 0.5-0.25mm particle size can greatly improve the flotation efficiency of low-rank coal. With the decrease of carrier particle size, flotation effect weakened. Meanwhile, the recovery rate of 0.5-0.25mm granular carrier reached 98.92%. Finally, strengthening mechanism of low rank coal flotation on the carrier were discussed.