In this study, microstructure and mechanical properties of 7068 aluminum alloy matrix nanocomposite reinforced with 0.1, 0.3, 0.5, 0.7 and 1 wt.% graphene nano plates (GNPs) produced by stir casting and ultrasonic treatment have been investigated. Ultrasound device equipped with a cooling system with high power was used for mixing alloy and nanoparticles. Also the microstructure was investigated by scanning electron microscope. The microstructural studies revealed that GNPs addition reduces the grain size, but adding high GNPs content (1 wt.%) does not change the grain size considerably. Further investigations revealed that the addition of GNPs increases tensile strength. At high GNPs contents (1 wt.%), the presence of GNPs agglomerates on grain boundaries were found that causes decrease the tensile strength. The optimum amount of nanoparticles is 0.5 wt.% GNPs. The average ultimate tensile strength (UTS) of the specimens before and after extrusion processes increases from 212 MPa to 374 MPa. Adding of 0.5 wt.% GNPs and extrusion process make about 76% enhancement in tensile strength compared to that of unreinforced aluminum alloy.