This study gives the problem of a crack in the film oriented perpendicular to the
film-substrate interface with the crack tip terminating at the interface. Based on Beuth’s theory,
three-dimensional model is simplified to plane strain problems, which obtains fracture mechanisms
of a cracked film-substrate medium by applying the boundary element method(BEM). The method
aptly resolves the problem involving stress concentration and, further, that this study develops the
multi-region boundary element method and applies it to evaluate the cracked film-substrate
medium. It shows that the stress intensity factor is affected by the different elastic mismatches and
the thickness ratio of the film and the substrate. These results indicate: 1) The stress intensity factor
has remarkable increased with the decrease of the thickness ratio of the film and the substrate. The
effect of the fracture behavior of film is negligible when the thickness ratio of the film and the
substrate is above 10, therefore, it is treated as thin film; 2) The stress intensity factor will decrease
with the increase of α ( −1 pα p +1) for β = 0 and β =α / 4 , where α and β are called
Dundurs parameters. What’s more, this paper studies the special condition of the film-substrate
medium, which is the analysis of the fracture of the absence of any elastic mismatch between the
film and the substrate, i.e.α=β=0, and revision of the formula of Xia and Hutchinson is put forward
for the stress intensity factor of the deep crack problems by comparing to the former conclusions of
Y.Murakami.