Abstract: Aiming at the problems of high moisture content and the difficulty in dewatering of fine low rank coal particles in the Boertai coal preparation plant,in this paper,the dewatering performance of low rank coal slime was evaluated by using inorganic salts and surfactants.The results show that the coal samples from Boertai coal preparation plant have the characteristics of fine particle size,great high-density content,abundant surface oxygen-containing functional groups,and high gangue content. When FeCl_3 and PAC are used to dewater coal slime,the filtration rate increases significantly by 0.129 and 0.113 mL/( s·cm~2) respectively,and the moisture content of filter cake decreases to a certain extent; when using surfactant,DTAC and Tween 85 accelerate the filtration speed greatly and reduce the moisture content of filter cake,the moisture content of filter cake decreases by 0. 69% and 1. 03%,and the filtration rate increases by 0. 301 and0.152 mL/( s·cm~2); in the mixture of inorganic salt and surfactant,the dehydration effect of non-ionic Tween 85 and anionic sodium oleate is significantly improved.When Tween 85 co-existes with FeCl_3 and PAC,the cake moisture decreases by 1.39% and 1.52% respectively,and the filtration rate increases by 0.044 and 0.040 mL/( s·cm~2),respectively. When sodium oleate co-existes with FeCl_3 and PAC,the moisture content of filter cake decreases by 2.79% and 2.61%,and the filtration rate increases by 0.026 and 0.021 mL/( s·cm~2),respectively. FeCl_3 and PAC can decrease the surface activity of DTAC,and have little effect on the surface activity of Tween 85,but can increase the surface activity of sodium oleate significantly. The results show that the existence of three surfactants can improve the surface hydrophobicity of low rank coal,and the addition of inorganic salts promotes the adsorption of anionic and non-ionic surfactants on the surface of low rank coal,thus enhancing the improvement of surface hydrophobicity of low rank coal.