In this work, the decomposition behavior of methane hydrate in porous media was investigated in the three-dimensional cubic hydrate simulator (CHS) using the huff and puff method with a single well, which is divided into three stories, distributed in the center line position of the reactor. The thermal huff and puff process is analyzed, and it is concluded that each huff and puff cycle includes three stages: heat injection, soaking, and gas production The injected heat spreads out from the injection point. The region impacted by heat diffusion enlarges as the number of huff and puff cycles increases and eventually reaches the largest impact region. After that, the region;impacted by heat diffusion is no longer increasing with continuous heat injection. The change characteristics of the injection temperature, pressure, resistance ratio, and other related parameters during the injection are obtained. The result also verifies that the hydrate decomposition process is a moving boundary ablation process in the three-dimensional level.