A mathematical model is firstly developed to describe the hydrate dissociation, in which the effects of the flow of multiphase fluid, the kinetic process and endothermic process of hydrate dissociation, ice-water phase equilibrium, convection and conduction are considered. Based on the model, the comparisons of production behavior between gas and gas hydrate reservoirs are presented. Numerical results show that the gas rate of gas reservoir is higher than that of gas hydrate reservoir under the same condition. However, the period of stable production of gas reservoir is shorter than that of gas hydrate reservoir. The water rate of gas hydrate reservoir is higher than that of gas reservoir. Moreover, the moment that the water rate rises to the maximum value is later with the increase of reservoir initial pressure. Results also show that the difference of cumulative gas volume between gas and hydrate reservoirs decreases with the increase of the initial pressure of reservoir. When the initial pressure of reservoir reaches a certain value the cumulative gas volume of gas reservoir exceeds that of gas hydrate reservoir. The pressure depletion in gas reservoir is faster than that of gas hydrate reservoir due to the permeability reduction caused by the solid gas hydrate.