The critical cracking and damage mode of titanium nitride films on pure titanium substrate at ambient temperature were investigated by the Cantilever Bending test. Acoustic Emission technique was employed for identifying the onset of the films fracture which occured with the load increasing when the inner stress of the films σf reached its ultimate strength σc or the shear stress at the interface τf reached the adhesion strength τc. In terms of the above criterions, the initial cracking of the film on the top occured at the inner of films when the load was increased to a critical value, i.e. Lct = 800gf; Whilst the cracking of the film on the bottom started along the interface at the critical load Lcc= 1285 gf. In addition, the feature of the cracking and spalling of the film has been discussed.