Selective laser sintered graphite part have low relative density, and its thermal conductivity is relatively low. In this paper, porous graphite preforms with densities ranging from 18.78% to 24.95% were prepared by selective laser sintering process with varied process parameters. Effective thermal conductivity of the preforms at room temperature was measured by transient plate heat source method. The effect of laser energy density between 0.05 and 1.5 J/mm2 on the thermal conductivity of the preforms was studied.Results showed that there was a positive correlation between laser energy density and thermal conductivity, and the relative density of preform increased with the increment of energy density when the energy density was less than 1.367 J/mm2, while the relative density of preform remained unchanged when the energy density is greater than 1.367 J/mm2. By introducing correlation coefficient between energy density and thermal conductivity, based on the thermal conductivity data of preforms prepared under different energy densities, a theoretical model of thermal conductivity related to laser energy density and thermal conductivity of porous graphite preforms was established, and the validity of the thermal conductivity model was verified by experiments. Results showed that the deviation between the predicted value of the heat conduction model and the measured value of porous SLS graphite preform is less than 1.5%.