Abstract: 【Objective】The desorption efficiency of coalbed methane is the key to efficient development. Macroscopic experiments are difficult to reveal the microscopic interface interaction mechanism between surfactant and coal rock, water and methane, which limits the in-depth understanding of the mechanism of enhanced gas recovery. 【Methods】 A coal-surfactant-water-methane composite system was constructed by molecular dynamics simulation. The adsorption behavior of three non-ionic surfactants (Tween80, Span80, OP4) on the surface of three coals (DJ_1, DJ_2, DJ2_2) and the regulation mechanism of methane desorption were studied. The simulation conditions are 353 K and 20 MPa. 【Results】 Surfactant forms an adsorption layer on the surface of coal rock through van der Waals action: Tween80 single molecule has more atoms and the strongest van der Waals force; span80 and OP4 have simple structure and are easy to enter the pore competition water level point. The surfactant weakens the interaction between methane and coal rock, which increases the free energy of methane adsorption and shallows the potential well, resulting in “thermodynamic repulsion effect”. At the same time, it competes for hydrogen bond sites, destroys the continuity of the water film, relieves the water lock effect, and improves the diffusion coefficient of water molecules. Radial distribution and number density analysis show that methane is “structurally exfoliated” from the adsorption layer as a free state. The free energy curve confirms that the surfactant has a universal repulsive effect on methane and has a coal-rock dependence on the effect of water (DJ_2, DJ2_2, the water molecular potential well deepens). The contact angle simulation showed that the contact angle decreased by 33 ~ 44 ° after treatment, and OP4 had the best effect in DJ2_2(from 59.5 ° to 15.5 °). 【Conclusion】 Surfactant adsorbs on the surface of coal rock through van der Waals action, competes for the hydrophilic water level point, reconstructs the coal-water interface, destroys the continuity of water film and relieves the water lock effect. Weaken the methane-coal rock interaction and strip the adsorbed methane; improve the wettability of coal rock and reduce the contact angle. The cascade mechanism of “competitive adsorption-water film destruction-wetting improvement-methane desorption” is realized, which provides a theoretical basis for the optimization and compound design of surfactants for chemical enhanced coalbed methane mining.