This work presents the study to explore the thermodynamic conditions of CO2 separation from the simulated integrated gasification combined cycle (IGCC) fuel gas via hydrate formation assisted by dimethyl sulfoxide (DMSO) and tetra-n-butyl ammonium bromide (TBAB). The measurements of the equilibrium hydrate formation conditions in the pressure range of (0.45 to 7.60) MPa and temperature range of (275.55 to 285.45) K were explored by the T-cycle method, and the gas phase composition at the equilibrium point was sampled and analyzed. In addition, the effect of DMSO upon CO2 hydrate and CO2 + TBAB was further investigated. The experimental results showed that while DMSO has a thermodynamic inhibition effect on the formation of CO2 hydrate, but a kinetic promotion effect on the solubility of CO2 in water solution, the mixture of TBAB and DMSO can reduce the pressure needed for CO2 hydrate formation obviously as well as promote the solubility of CO2 remarkably.