Abstract: In order to provide a theoretic basis for the research of Ti(C_xN_y) thin films, the thermodynamic database of Ti-C-N ternary system is established and the phase diagram sections are calculated. In addition to the assessed thermodynamic properties of Ti-C-N system, the influence of the residual strain energy of Ti(C_xN_y) thin films on the phase equilibria is analyzed. The classical formula for calculating the elastic strain energy is expressed into a Redlich-Kister form in order to perform the thermodynamic and equilibrium calculations using the Thermo-Calc software. Isothermal sections at 900 and 1100 K are calculated with this database and compared with those calculated without considering the residual stress. As a result, with the addition of strain energy δ-fcc Ti(C_xN_y) phase area shrinks. It is therefore concluded that with the influence of the residual stress in Ti(C_xN_y) thin solid film, the precipitation of pure δ film requires more precise control of composition.