The cohesive zone interface model was used to calculate 90o peel in the ACF bonding samples. The constitutive equation for the interface model was modified by introduction a damage factor χ . The thermal damage factor and humidity damage factor can be derived from the experiment data. The interfacial model with damage factor can change the maximal peel stress and the delamination length. The calculation result of the interfacial model with damage factor agreed well to the experiment of the 90o peeling.