Abstract: In the selective laser sintering(SLS) process,the low intensity and high porosity of the sintered part are still the key factors that restrict the industrial progress of the SLS technique.The interaction between the laser and the materials and the distribution of the three-dimension temperature field are important factors that affect the densification of the sintered part.They are also the essential basis for choosing the appropriate SLS process parameters.The interaction between the infrared laser and the polymer materials had been discussed in this paper.A numerical simulation model for SLS process is presented,which has been used to analyze the densification of the sintered part.The simulation results accord with those of the experiments.The results show that the SLS model can be used to estimate the densification of the sintered part effectively.