Abstract: Nylon 12-coated aluminum composite powders with different aluminum contents were prepared. The morphology and the thermal properties of the composite powder were characterized by SEM，EDX，DSC and TG. Specimens were fabricated by selective laser sintering (SLS)，then the effects of the aluminum content on dimensional accuracy and mechanical properties of the sintered part were studied. The results show that there is strong interfacial adhesion between nylon and aluminum powder，the nylon is melted during the sintering process and aluminum powders are dispersed uniformly in the nylon matrix. As the aluminum content increases，the flexural strength and modulus of the sintered part increase remarkably，but the impact strength decreases gradually. With 50 wt% aluminum content，the flexural strength and modulus of the sintered part are improved by 62. 1% and 122. 3%，respectively，compared to the sintered part of nylon powder. The increasing of aluminum content would effectively restrain the shrinkage of the nylon matrix，and enhance the dimensional accuracy of the sintered part .