MD simulations are carried out on the sI CO2-CH4 mixed hydrates in the constant-NVT and constant-NPT ensembles for the two cases of CO2 occupancy. One is 75% called normal, the other is 87.5%. The simulations results show that the hydrate structure can be maintained both for the two hydrates over the temperature range of 0K to 300K. However, the equilibrium pressure, the potential energy and the MSDs of the atoms in H2O for the higher CO2 ratio hydrates is larger than that of the normal CO2 ratio hydrates, indicating that the normal mixed hydrates is more stable than the higher CO2 occupancy mixed hydrate. These results are consistent with the present experimental results.