Thermal cycling conditions are among the most sever environmental conditions for composites and have a great effect on the micromechanical properties near interfaces.An AFM(atomic force microscope)-based nanoindentation method was employed to measure the nanohardness and the plastic deformation capacity near interfaces in graphite fiber reinforced aluminum alloy matrix composites(Gr/Al)after thermal cycling.With increasing of thermal cycles, the nanohardness values of both fibers and the matrix decrease and the plastic deformation capacity of the matrix increases.Both of the changes in the nanohardness and the plastic deformation capacity are dependent of the distance to the fiber-matrix interface.Changes in nanohardness can provide important information about residual strains because the local elastic or plastic residual strains have effects on the local hardness.