Using the non-equilibrium Green's function method together with the density-functional theory, the current-voltage (I-V) characteristics of armchair and zigzag graphene nanoribbons (GNR) have been evaluated. It is found that the strain effect on the GNRs is periodically changed with the GNR width of 3. The conductivity of GNRs under compressive strain changes a lot, which is associated with the buckled configuration. In addition, the transport properties of elongate GNRs are changed due to the difference in the electronic structures of C atoms. (c) 2013 Elsevier B.V. All rights reserved.