In order to determine the absolute hardness of film or coating, it is necessary to separate the different contributions. It is known that, depending on the thickness of the film and on the applied load, indentation measurements give apparent hardness values which are the results of contributions by both the substrate and the film. There is a need therefore to separate these two contributions in order to determine the true hardness of the film. Numerous authors have worked on this subject during the past and a large number of models who are written under an additive linear function are available in the literature. This study is to determine the absolute hardness of nitride thin layers obtained by two activation rate plasma of 50 and 65%. A series of classical Vickers indentation at several loads were applied at the surface of the specimens. The true hardness of these thin films was determined by using monolayer model of Jonsson and Hogmark which gives in general cases the concluded results.