Abstract: Solid autogenous pyrolysis plugging technology is an innovative technology which is suitable for relieving hydrate plugging in wellbore. A mathematical model of phase equilibrium, decomposition rate and decomposition heat transfer of hydrate was established to solve the problems of heat release diffusion and loss during the reaction of autogenic pyrolysis plugging agent. The study of heat diffusion simulation was carried out at different concentrations and diameters, and the distribution cloud maps of wellbore temperature, water volume fraction, natural gas volume fraction and hydrate volume fraction were obtained under different conditions. The research shows that with the increase of concentration of autogenous pyrolytic plugging agent, the rate of heat release accelerates, the heat transfer to the surrounding area increases, and the heat diffusion is irregular. With the increase of wellbore diameter, the time of pyrolysis plugging increases, and the amount of autogenous pyrolysis plugging agent also increases. In this paper, the fitness of simulated calculation value and actual value is more than 85%, which provides a theoretical guidance for on-site plugging remove operation.