CO2-ECBM is capable of realizing CO2sequestration and coalbed methane (CH4) production simultaneously. Practical coal seam contains H2O, thus significantly influencing adsorption, desorption, diffusion, and flow capability of CO2and CH4. Accordingly, the impacts of H2O on adsorbed CH4on coal displaced by CO2were investigated to gain a further understanding on CO2-ECBM. The results derived from this study indicate that the occurrence of H2O with coal positively relates to oxygenic functional groups and mesopores of coal. Particularly, the oxygenic functional group of the coal matrix acts as a primary adsorption site for H2O. The mesopore of coal is the main space for H2O occurrence. Furthermore, the impact of H2O on CO2adsorption on coal depends on dissolution capability and competitive adsorption of H2O. With respect to coal with a low H2O content, the dissolution of CO2in H2O is dominant at high CO2adsorption equilibrium pressure, thus leading to increasing CO2adsorption capability of coal, while the opposite trend is applicable for coal with a high H2O content. With regard to the displacement process, injecting CO2promotes desorption of adsorbed CH4from dry and moist-equilibrated coals. The absolute adsorption amount of CO2at the equilibrium state for displacement is lower than that in single-component adsorption for both dry and moisture-equilibrated coals at equilibrium pressures below 3 MPa, whereas the adverse trend exists for a high equilibrium pressure range of 3–4 MPa. Moreover, the elevated CO2injection pressure favors both CO2adsorption and CH4desorption on dry and moisture-equilibrated coals. The presence of H2O decreases the CO2adsorption amount and CH4desorption amount of the coals. Therefore, practical implementation of CO2-ECBM should focus on the H2O dependence of CO2sequestration and CH4recovery.