The kinetics of gas hydrate formation and decomposition at the gas water interface are of crucial importance to the application of the hydrate-based technique and the gas recovery process from marine sediments. Herein, the behaviors of in situ CO2 hydrate growth and dissociation at the interface of liquid CO2 and water were observed using magnetic resonance imaging. The results indicated that the growth of the hydrate film was primarily controlled by the mass transfer of CO2 into the water phase. Notably, the stepwise depressurization beyond the equilibrium pressure was found to facilitate the thickening of hydrate films as a result of the enhanced evolution of dissolved gas out of water for hydrate formation. The addition of surfactants (sodium dodecyl sulfate) could contribute to a shorter induction time and a thinner hydrate film. The dissolution of the gas molecule and bubbles in the water phase were suggested as the crucial factor impacting the thickening of CO2 hydrate films.