The temperature fields of powder laser sintering have a direct influence on optimization of process parameters and sintering quality. From three-dimensional heat transfer of point source, three-dimensional analytical model of non-steady-state temperature field for scanning laser sintering was established. With the moving Gauss area heat source, effective thermal conductivity of nylon powder with temperature changed was calculated. The expression of thermal diffusivity and laser energy was obtained. Finally, by simulation and theory of temperature field, validity of the model and parameter fitting was verified.