In this study, Si3N4 (varying from 0 to 12wt.%) or SiC (varying from 0 to 30wt.%) reinforced aluminum matrix composites were fabricated by powder metallurgy method. The effects of reinforcement element (SiC or Si3N4) addition on the mechanical properties of aluminum composites were newly examined for large-scale distribution. Microstructures and crystal structures of composites were analyzed via scanning electron microscope (SEM) and X-ray diffractometry (XRD), respectively. Density, hardness and compressive strength of composites were tested by density meter, micro Vickers hardness tester and universal test machine. From the experimental results, it was observed that the hardness value of pure aluminum was obtained 30 HV. Also, the highest hardness values were obtained at Al-9%Si3N4 (57 HV) and Al-30%SiC (79 HV) composite. Similarly, the highest yield and ultimate compressive strength were determined at Al-30%SiC and Al-9%Si3N4 composite. Pure Al, Al-30%SiC and Al-9%Si3N4 were measured as 82, 138, 198 MPa and 113, 224, 292 MPa, respectively. Increased to weight percentage of Si3N4 from 9% to 12% in Al-Si3N4 composites, the apparent density, Vickers hardness and compressive strength of Al-12 wt.%Si3N4 composite sharply decreased due to the agglomeration of Si3N4. As a result, it has been observed that SiC or Si3N4 addition makes a positive contribution to the mechanical and microstructure of aluminum composites. These composites should be used for the wear application of aluminum.