Abstract: The bulk polystyrene/Al2O3 nanocomposites were successfully prepared by selective laser sintering (SLS) process.The SEM micrograph showed that the nano-sized Al2O3 particles were uniformly located within polystyrene matrix.The effect of process parameters,laser power and scan velocity,on the sintering behavior of the mixture powders was studied by means of experimental and microstructural investigations.The mechanical properties were compared between the sintered specimens from polystyrene/nano-Al2O3 mixed powder and pure polystyrene powder under the same process conditions.Notched impact strength of the nanocomposite parts showed 20%~50% higher than that of the pure polystyrene parts,the maximal value was found to be 10.1kJ/m2,but Rockwell hardness increased only 5%.