The long term stability of CO₂ hydrate is an essential respect for the CO₂ storage on the ocean floor. The potential diffusivity of CO₂ molecule will, however, exist in the hydrate due to the great differences of CO₂ concetration at the interface between the sea water and the hydrate, and the consequent CO₂ diffusion transfer into the ocean is expected. Behavior of CO₂ in the sea water after emission and dissolution from the hydrate deposit or liquid CO₂ pool has an important influence on the benthic environment In this paper the diffusion and its rate of CO₂ in the hydrate were presupposed and the transient diffusive and advective transfer of CO₂ in the sea water were analyzed under the steady sea water current. Computed CO₂ concentrations, velocity vectors and the consequent pH distributions were indicated at the representative time steps.