Abstract：Low-rank power coal contains more fine-grained and clay minerals, which leads to its increased filtration difficulty. In this paper, anionic polyacrylamide (APAM) and cetyltrimethylammonium bromide (CTAB) were selected as filtration aids to enhance coal slurry filtration. Low-field NMR technique was used to detect the pore changes of the filter cake, and zeta potential meter, focused beam reflectometry, contact angle meter, surface tension meter and X-ray photoelectron spectroscopy were used to characterize the coal particles and filtrate properties. The results showed that the filtering aid improved the filtration rate and reduced the cake moisture, CTAB significantly improved the hydrophobicity of coal surface and reduced the surface tension of filtrate, but only increased the cake porosity by 2.65%, APAM significantly reduced the particle zeta potential and increased the floc size by about 7-9 μm, which increased the cake porosity by 11.65%. In summary, the mechanisms of APAM and CTAB to strengthen coal slurry filtration and dewatering are different, CTAB mainly promotes coal slurry filtration and dewatering by "lubricating" the pore wall of the filter cake and enhancing the hydrophobicity of the pore wall, while APAM mainly strengthens coal slurry filtration by weakening the electrostatic repulsive force between particles and promoting the formation of flocs to increase the pore rate of the filter cake.