Abstract: The in situ properties of components including the epoxy matrix, the carbon fiber and the interlayer of the carbon fiber/epoxy composites were examined by the nanoindentation. The hardness, Young’s modulus and creep behavior of the components in the composites were obtained. The results show that the hardness and Young’s modulus have a gradient variation from the epoxy matrix to carbon fiber. Compared with the intrinsical value, the in situ Young’s modulus of the fiber has a decline, and the Young’s modulus of the matrix exhibits an enhancement. The in situ properties are influenced by the surface residual stress due to mechanical grinding of the specimen and the interaction of the components of the composites. Moreover, a remarkable change of creep behavior at the transition zone from the fiber to the epoxy matrix is found in the present nanoindentation tests.