The pressurized entrained-flow gasification is the most efficient and promising technology for utilization of lignite, where dense-phase pneumatic conveying under high pressure is one of the key techniques. The study aims at clarifying the conveying mechanisms of dense-phase pneumatic conveying of pulverized lignite in horizontal pipe under high pressure. For this purpose, bulk density of pulverized lignite with different moisture content was measured and analyzed, and the quantitative relationship between interparticle cohesion/cohesive forces and the moisture content was obtained. On the basis of this quantitative relationship, Mohr-Coulomb yield criterion was introduced to quantify particle flowability, and Castellanos's model was introduced to evaluate the fluidization characteristics. Combined with particle flowability and the fluidization quality, the conveying mechanisms of dense-phase pneumatic conveying of pulverized lignite in horizontal pipe under high pressure were explored. Results indicated that when the supplementary gas flow rate rises, the conveying capacity becomes weak, and the conveying resistance shows a decreasing firstly and then increasing tendency. While when the moisture content rises, the conveying capacity becomes weak, the conveying resistance strengthens, and the conveying stability weakens. (c) 2020 Elsevier B.V. All rights reserved.