Due to extensive applications of the thin film/substrate systems in engineering, the research on strength, ductility and reliability of these systems have attracted great deal of interest in recent years. The peel angle of debonded film on the ceramic substrate has a very important effect in the mechanical resistance of film/substrate bi-material. Among critical debonding parameters, peeling angle and thermal residual stresses can be a potential risk of brutal propagation causing the film/substrate composite failure under tensile loading. This study is carried out to analyze the peeling angle and residual thermal stresses effects with crack growth in the specimen. A two dimensional elastic-plastic finite element model is used to compute the J-integral and estimate the plastic zone size at the interfacial crack tip of film/substrate composite. Results show that the peeling phenomena is a fracture mixed mode where the dominance of either mode I or mode II is influenced by the peeling angle while delamination of thin film is greatly dependent on thermal residual stresses.