Abstract: Phase transition and migration of moisture during coal spontaneous combustion have a significant influence on the environment of heat conductivity and the accumulation of loose coal,at the same time,the changes of thermal conduction properties of loose coal can be directly expressed by heat conductivity coefficient. As water transition has practical effect on the humid-warm transition during the spontaneous combustion of loose coal,this paper built a sim-plified physical model of moisture loose coal,using finite element simulation to calculate the temperature and heat flux distribution during phase transition,analyzed the change of thermal conductivity of moisture loose coal with phase tran-sition and then obtained its relevant heat conductivity coefficient. The results show:The water phase transition directly affects the internal distribution of temperature and heat flow in moisture loose coal, and finally brings the overall change of the thermal conductivity;Based on the influence of the water phase transition,the thermal conductivity of moisture loose coal increases linearly along with the saturation-degree of liquid phase,and the increasing trend gradu-ally slows down with the increase of temperature;The relationship between the thermal conductivity and the liquid sat-uration at 100 ℃ is as follows:λe = 0. 130 1+0. 132 8S,the reliability of the simulation is verified by the error analysis of the results and the comparison data.