Objective To study the stress of TiN coating/ Ti alloy substrate system under contact load. Methods A credible finite element analysis model was established based on ABAQUS, and the contact stress of TiN coating/ Ti alloy substrate system with different coating thicknesses was analyzed in detail under the normal load of a sphere indenter. Results The maximum Mises stress of TiN coating/ Ti alloy substrate system occurred at the sub-surface located about 0. 4a (a is the contact radius) below the surface or at the interface near the sub-surface. Because of the contact and bending stress, the bending deformation of TiN coating affected the radial and shear stress distribution of TiN coating. Conclusion Both contact stress and bending stress were found in the TiN coating/ Ti alloy substrate system under contact load, and the results are helpful for understanding the failure mechanism of TiN coating/ Ti alloy substrate system.