In oil-gas-water three-phase systems, CO2 can be distributed either as a non-wetting or intermediate-wetting phase. The morphology and distribution of CO2 clusters under different wetting sequences are different, which has a complex influence on CO2 dissolution process. Based on phase distribution obtained from the three-phase flow experiment, we constructed the physical models of initial CO2 phase distribution. Subsequently, we simulated the CO2 dissolution process when CO2 is non-wetting phase and intermediate-wetting phase based on the VOF framework and CST method. The dynamic evolution of CO2 clusters and dissolved CO2 distribution during dissolution process was tracked. The effect of wettability on CO2 dissolution trapping in three-phase systems was revealed. The characteristic parameters of CO2 dissolution process were also analyzed quantitatively. Our results show that CO2 clusters exhibit different dissolution states under different wettability conditions in three-phase systems. When CO2 serves as the intermediate-wetting phase, the initial phase distribution is more dispersed, and the size of CO2 clusters is smaller, the CO2 saturation decreases more within the same period, indicating that CO2 has a higher dissolution ability. The initial CO2 saturation determines the final CO2 concentration in the other phase. Dissolution causes the originally connected large CO2 clusters to decompose into multiple small clusters. When CO2 serves as the intermediate-wetting phase, the mass of dissolved CO2 is higher, and thus the dissolution ability is higher.