The nano Al2O3 -Cu/Cr composite was prepared by a simplified internal oxidation technique of the vacuum hot-press sintering-internal oxidizing method. The tensile strength and microhardness were determined respectively. The microstructures were analyzed by means of a scanning electron microscope (SEM). On the basis of above results, the main strengthening mechanisms were investigated by quantitative calculation of several strengthening effects. The experimental results show that the microhardness and tensile strength obviously increase with increased cold deformation. The main strengthening mechanisms of the nano Al2O3 -Cu/Cr composites are mainly attributed to the dispersion of the nano-scale of alumina particles and the aggregate of the Cr particle phase, of which the former can restrict the mobility of the dislocations and increase the density of dislocations. Meanwhile, the cold deformation strengthening has some important effect to a certain extent.