The adsorption behaviors of CH₄ and CO₂ on moist kerogen are vital to understand the process of CO₂sequestration and shale gas exploitation. In this work, a realistic type II dry kerogen model was constructed and optimized by the molecular dynamics (MD) method. Then moist kerogen models with various moisture contents (0.7 wt.%, 1.4 wt.%, 2.1 wt.% and 2.8 wt.%) were developed by Grand Canonical Monte Carlo (GCMC) simulations, and the adsorption characteristics of CH₄, CO₂ and their mixtures on these kerogen models were investigated. Based on the influences of moisture content on the adsorption capacity, isosteric heat of adsorption and adsorption selectivity of gas molecules, the potential feasibility of CO₂ sequestration and enhanced shale gas recovery was discussed. Results show that water molecules are prone to aggregate into cage cluster structures at high moisture content, worsening the replacement effect of CH₄ by CO₂. The development effect of shale gas reservoirs with CO₂ sequestration is better at low reservoir pressure. Moreover, the development effect for CO₂ replacing CH₄ can be improved by increasing the kerogen moisture content at low moisture conditions. For a shale gas reservoir with higher thermal maturity, it can be beneficial to inject some mixtures of CO₂ and a certain amount of steam at the late development stage in order to enhance the shale gas recovery.