Abstract: An ultra micro-indentation system for investigating plastic and elastic properties of hard coatings and near-surface materials is described. The microhardness and Young’s modulus of the materials are derived from records of loading and depth of penetration. The load can be controlled less than 0.1mN and depth of penetration is measured with a resolution less than 1nm. The instrument can also distinguish plastic and elastic deformation so that the accuracy and precision of the obtained hardness data is greatly improved. Determination of the depth distribution of hardness can be carried out in one single indenting process. The plastic and elastic behaviors of TiN, TiB₂, DLC and CN films are studied in the present work. Finally, one practical application of the system in coating engineering is reported.