Abstract: Abstract: To solve the problem that lignite is difficult to prepare high-concentration coal-water slurry, pressure pretreatment is adopted to increase slurry concentration, and the mechanism of pressure action on improving slurry concentration of lignite is discussed. The results show that pressurized pretreatment can reduce water content, specific surface area and pore volume of lignite. With the increase of pressure, the slurability of lignite increases. When the pressure is 150KN/cm, the maximum slurry concentration reaches 53.1%, which is 5.1% higher than the raw coal.