Multiple channels data collecting instrument has been used to investigate the temperature distribution of melt-cast explosive during the cooling process under various cooling conditions. The most valuable inflexion point of the temperature curve was obtained during the cooling process, especially at the moment when the phase transformation occured. Through the analysis of the experiment data, the mechanism of the phase transformation and that several temperatures of the phase transformation of melt-cast explosive were obtained. Phase transformation temperatures tend to decline along with the increase of the content of melt-cast explosive. Phase transformation temperatures are 76-77 ℃,which are both under the TNT melting point.