Methane hydrate dissociation is studied using numerical and experimental approaches for a low carbon dioxide (CO2) emission power generation system utilizing methane hydrate. A novel power generation system has been proposed by authors, in which methane gas produced from oceanic methane hydrate reservoir by thermal stimulation method is used as fuels. The performance of the power generation system and the heat loss during the injection of hot seawater to the methane hydrate layer were investigated in previous study. However, the estimation of the methane gas production rate from the methane hydrate reservoir is necessary to evaluate the performance of whole system. In this study, we conducted the numerical simulation of methane hydrate reservoir. In order to evaluate the reaction rate of methane hydrate dissociation, the methane hydrate formation and dissociation experiment was conducted. The result of numerical simulation indicates the necessity of improvement of the production process to supply the heat of hot water effectively. From the experimental result, it comes to see that consideration of the scale effect of the methane hydrate construction is necessary to describe the dissociation rate.