Carbon nanomaterials (such as graphene, carbon nanotubes and nano-diamond) are widely used to synthesize metal matrix composites to strengthen metals such as Ti, Al and Cu. However, severe aggregation of these nano-scale reinforcements within the metal matrix has been a serious issue to achieve good performance metal matrix composites. In this study, we employed an in-situ co precipitation method to decorate reduced graphene oxides with aluminium oxide nanoparticles (i.e. rGONs@Al2O3), which were then introduced into Ti 6Al-4V matrix using the processes of ball milling and spark plasma sintering. Effects of co-precipitation temperature on the characteristics of rGONs/Al2O3 nanopowders, and their concentrations on microstructures and mechanical properties of the composites were systemically investigated. Characterization results revealed that γ8 Al2O3 nanoparticles were uniformly wrapped with rGONs fakes, and numbers and sizes of Al2O3 nanoparticles were decreased with the increase of co-precipitation temperature. The rGONs@Al2O3 nanoparticles were uniformly coated onto the surfaces of the Ti-6Al11 4V powders, thus achieving a much finer grain size of matrix after the sintering process. As the content of rGONs@Al2O3 was increased, the strength of the composites was enhanced, whereas the elongation was slightly decreased. Due to effects of grain refinement and effective load transfer, the composite of 0.5 wt% rGONs@Al2O3 has achieved a high yield strength and an ultimate tensile strength of 950 MPa and 1022 MPa, which were ~120.4% and ~117.1% of the TC4 matrix, respectively. The fracture morphology was a mixture of cleavage fracture and ductile fracture.