In this study, we have investigated a gas production system from methane hydrate layers using hot water injection using horizontal wells including a production well and multiple injection wells. Experiments on the gas production were performed using scaled two-dimensional physical models to investigate fluid flow characteristics and production performance. Furthermore, experiments on an improved production system by hot water injection using multiple injectors have been carried out. It has been shown that gas production rate can be improved by hot water injection using the multiple horizontal injectors compared with that with a single horizontal injector for thick hydrate layers of over 15 meters. The numerical simulations have been done on the field gas production performances by hot water injection with multiple injectors which are drilled in a hydrate layer of 15 meters in thickness. The cumulative gas production for three years with 1000 ton/day of hot water injection was evaluated at the end of three years as 8×106 std m3. The system using multiple injectors is appeared to be more economical procedure than that with the single injector. Furthermore, a synthetic gas production system has been presented in considering of a gas turbine combined thermal cycle which can provide dissociation heat of methane hydrate by waste heat of its exhaust gas.