In this paper, GNPs/Al composites were prepared by mechanical stirring and sintering method. The complete spreading of non-destructive GNPs and uniform distribution of GNPs in aluminum matrix were realized. The effect mechanism of GNPs on the densification behavior of composite powder during cold pressing and sintering was studied. The effect mechanisms of GNPs on the strength and plasticity of composite was clarified. The effect of sintering time on the mechanical properties of GNPs/Al composite was discussed. The results showed that the relative density of sintered GNPs/Al composite was more than 98% when the content of GNPs was less than 0.5%. The yield strength of as sintered Al-0.5wt.% GNPs reached 204 MPa, which is 18.6% higher than that of pure aluminum. Taking Al-0.5wt.% GNPs as an example, after sintering for 6h, the hardness of the composite was 61.5HV and the yield strength was 173 MPa. No obvious failure occurred at the compression strain being 40%.