A gas hydrate is an inclusion compound formed by the interactions between water and relatively low molecular weight gases under appropriate conditions, i.e., low temperatures and high pressures. On the basis of differences in the sizes and shapes of the cavities of gas hydrates, they have been classified into three common families: structures I, II, and H. Each structure gives rise to different lattice dimensions for optimal guest occupancy. On the basis of the size ratio of the guest relative to the cavity, occupancy of the hydrate cage by guest molecules may be selective. In this study, the selective enclathration and occupancy of gas hydrates were evaluated from the mixed CO2-N2O gas used. The hydrate-liquid water–vapor (H-LW-V) equilibrium line of CO2 and N2O were determined using a high-pressure equilibrium cell equipped with a magnetic driver and stirrer. Furthermore, CO2 and N2O were analyzed using Raman spectroscopic respectively. By using Raman spectroscopic, X-Ray Diffraction and Gas Chromatography, we reveal the mixed CO2-N2O gas hydrate formed a structure I clathrate hydrate. And we define the selective enclathration and occupancy of mixed CO2-N2O gas hydrates. This research is expected to provide basic knowledge pertaining to gas composition in the hydrate phase under different conditions.