Metal matrix composites(MMCs) reinforced with hard particles have many potential application in aerospace structures, auto parts, semiconductor package, heat resistant panels, wear resistant materials and so on. In this work, the effect of SiC partio sizes(50 and 100㎛) and additional elements such as Si, Cu and Ti on the microstructure and the wear property of Al-5Mg-X(Si, Cu, Ti)/SiC_p composites produced by pressureless infiltration method have been investigated using optical microscopy, scanning eletron microcopy(SEM) with EDS(energy dispersive spectrometry), hardness test, X-ray diffractometer(XRD) and wear test. In present study, the sound Al-5Mg-X(Si, Cu, Ti)/SiC_p(50 and 100㎛) composites were fabricated by pressureless infiltration method. The Al-5Mg-0.3Si-O.1Cu-O.1Ti/SiC_p composite with 50㎛ size of SiC particle has higher hardness and better wear property than any other composite with 100㎛ size of SiC particle produced by pressureless infiltration method. The hardness and wear property of Al-5Mg/SiC_p(50 and 100㎛) composites were enhanced by the addition of Si, Cu and Ti in Al-5%Mg matrix alloy.