: The main purpose of this research was to study the thermal properties of powders in selective laser melting process. Therefore, three different types of powders, i.e. 314S-HC stainless steels, M2 Gas atomized and M2 water atomized, were first subjected to a low power carbon dioxide laser and the temperature were experimentally measured at a specific location using a K-type thermocouple. The measurements were then used to calculate the thermal conductivity and the laser energy absorptance of the powders at room temperature assuming that the total volume of powders was a continuum. Knowing those properties is required for the simulation as well as analytical study of the process. In order to evaluate the accuracy of the calculated parameters, the calculated thermal conductivities and laser energy absorptance were used to predict the temperature distribution using ABAQUS commercial finite element package. DFLUX user subroutine was developed using FORTRAN programming language to model the moving laser heat source in the finite element simulations. The finite element predictions during heating as well as cooling were then compared with the experimentally measured temperature versus time. A relatively good correlation were observed between the experiment and simulation suggesting that the calculated parameters presented a reasonable estimation of the powders In practice, the phase change of powder particles from solid state to the molten state results in a dramatic change in porosity of the material. This in turn leads to a sudden change in both thermal conductivity and absorptance. So, those models that do not take the phase change into account, such as the one used in the first part of this study, are not expected to accurately describe the thermal properties of powders in selective laser melting process. It should emphasized that both the laser power and pulse on time was chosen to be very small to make sure that the powder did not melt. In an attempt to take the melting phenomenon into account and study its influence on the thermal properties of powders, FLUENT commercial package was used. So, the powder particles were individually modeled and the air between them were also considered using the patch capability in FLUENT software.thermal properties. A heat flux large enough to melt the powder particles were imposed as the boundary condition. The melt pool size was compared with the previously published predicted and experimental data. The comparison showed that the melt pool size prediction significantly improved when the phase change was considered in the simulation. Finally, the effect of process parameters, e.g. the laser power and scan velocity, were also studied using the FLUENT model. Keywords: Powder, Selective Laser Melting, Thermal Properties, Phase Change.