Abstract: The reservoir permeability is an important factor affecting the hydrate decomposition under depressurization combined with heat injection. Through establishing a 3D model of hydrate combination decomposition method including conservation equations, reaction dynamics equations and auxiliary equations, the combination method of hydrate decomposition under different initial reservoir permeability conditions has been reached, investigating the changes of pressure, hydrate decomposition and gas and water saturation. The results show that the higher the reservoir permeability is, the faster the pressure propagation velocity is; the lower the reservoir pressure level is, the smaller the flow hindrance is; the smaller the loss of heat injection is, the shorter the reaction time is; the greater the relative permeability of liquid phase is, the stronger the liquid phase fluidity is. But the reservoir permeability has a little effect on the change of gas saturation.