We employed the grand canonical ensemble Monte Carlo method and molecular dynamics simulations to study the adsorption and diffusion processes of CH? and CO? in a coal molecular structural model under different temperature, pressure and moisture content conditions, in order to investigate the adsorption and diffusion characteristics of CH? and CO? in coals. The results indicate the following: (1) As temperature increases or moisture content rises, the adsorption amounts of both gases decrease to a certain extent; however, CO? exhibits superior adsorption and diffusion capabilities compared to CH?; (2) As pressure increases, the adsorption amounts of both gases increase, but they tend towards saturation and exhibit typical saturated adsorption characteristics; (3) Langmuir model fitting results show that increases in temperature or moisture content lead to decreases in the adsorption parameters a and b. The CO? parameters remain higher than the CH? parameters, indicating a stronger adsorption affinity in coal. (4) Diffusion patterns show that an increase in temperature significantly enhances the kinetic energy of gas molecules, reducing local enrichment in coals and improving diffusion performance. The mean square displacement of CO? at all temperatures is greater than that of CH?, indicating stronger diffusion ability and a more uniform spatial distribution. (5) As the moisture content increases, the average mass density of both gases decreases in the coal molecular structure model. Although the presence of water molecules does not alter the overall trend of the gas adsorption curve, it significantly reduces the adsorption saturation point of the gases; (6) When the moisture content reaches 6.55%, gas diffusion behaviour is significantly inhibited. Water molecules fill the pores and interact with coal molecules, limiting gas diffusion pathways, reducing gas migration extent, and thereby restricting diffusion rates. The diffusion coefficients for CH? and CO? decrease to 0.063-8 m2/s and 1.33×10-8 m2/s, respectively. This study provides a theoretical basis for enhancing coalbed methane recovery rates and optimising CO? sequestration strategies.