Graphene reinforced copper composites were fabricated by a one-step chemical reduction and spark plasma sintering. The effect of graphene content on microstructure, mechanical properties and electrical conductivity properties of composites was investigated by XRD,SEM,Raman spectrometer, tensile testing machine, nanoindentation, eddy current conductivity meter, etc. The results show that graphene is uniformly distributed within copper matrix and can evidently improve the mechanical properties of copper matrix. Compared to pure copper, the yield strength, tensile strength and elastic modulus of composites is enhanced by 219.8%, 35.9% and 6.9% separately with addition of only 0.025% (mass fraction) graphene oxide. Besides, the electrical conductivity of composites remains 93.1%IACS. With the increase of graphene content, the yield strength, tensile strength and elastic modulus of composites decrease. The main reason is that graphene is not well wrapped by copper particles with the increase of graphene content and the bonding between the naked graphene and copper matrix is poor, which weakens the strengthening effect of load transfer.