Presence of porosity and gas layers around the Al2O3 particles are one of the most important reasons of decreasing in mechanical properties of aluminum metal matrix composites. In this research, for decreasing of porosity, increasing of wettability and uniformly distribution of particles in matrix three method were used; using inert gas for injection powder with 5 liter/ min flow rate, particles heat treatment in 1100 ̊C for 20 min and mill Al2O3 particles with Al particles in ratio of Al / Al2O3= 1. The effect of these parameters on microstructure and mechanical properties of composite were investigated. The results showed that amount of porosity and agglomeration of particles were high in metal matrix composite with handy injection of particles. While injection with inert gas, using heat treatment and Al / Al2O3 milled Cause improve wettability and uniformly distribution of particles in molten Al. the results showed the maximum value of hardness , compression strength and impact energy have obtained in metal matrix composite reinforced with Al / Al2O3 milled with value of 78.7 BHN, 539.1 MPa and 8.2 Joule, respectively.