Gas hydrate is encountered in reservoir rock at low temperature and high pressure circumstances. Exploitation gas hydrate commonly invokes to heating or reducing pressure, leading the solid phase transited into liquid phase. With phase transition, the heat is transferred not only in the form of specific heat but also in the form of latent heat. Moreover, the melting point is not constant but depends on the pore size for the phase transition in porous solid. Considering these characteristics, a governing equation of heat transfer with phase transition is established using the equivalent heat capacity method. The equivalent heat capacity is assessed by the pore size distribution curve. Heating tests are conducted and simulated using the model established. The process of heat transfer and its dependences on temperature are discussed.