Abstract:The 3-Dimention finite element model was founded and interface element was employed to simulate the characteristic of the interfacial agent at the jointing position, drawn the relationship curve between the characteristic parameter of the jointing interfacial agent and the critical adhesive strength, obtained the critical adhesive strength value of the jointing interfacial agent under symmetrical load, shows that the required critical adhesive strength decreases when the maximum opening displacement of the adhesive interface at failure point increases.