Thermal stimulation on dissociation of methane hydrate was investigated with molecular dynamics simulation. The dissociation mechanism of methane hydrate with structure Ⅰ was investigated systematically by injecting heated, liquid water of 340 K. The results showed that when the water molecules on hydrate surface are made in contact with high temperature liquid water, they obtain heat energy, and with the obtained energy the water molecules move intensively, breaking the hydrogen bond between water molecules, and destroy the clathrate structure. In addition, methane molecules that have obtained heat energy, break away from the clathrate and diffuse into liquid. Due to heat energy being transferred into inside layer from outside layer through collision between molecules, the hydrate is dissociated layer by layer. Comparing the effects of liquid water with different temperatures of 340 and 277 K on hydrate dissociation, it is concluded that the thermal stimulation promotes dissociation of the hydrate.