Abstract: According to the relationship between interface dilation and mode Ⅱfracture energy, a new way of constructing traction-separation law with dilation was presented. The method, by first assuming the mode Ⅱ traction-separation relationship, and then deriving the interface dilation, was easier to apply. Defining four damage variables based on the interface separation and fracture energy, traction-separation laws with dilation considering damage effects were further given. This enables the model to simulate not only the monotonic loading problems but also reversed loading problems. In addition, interface tangential bonding strength, normal separation, and friction effect under interfacial pressure were discussed respectively, which led to corresponding computing methods or recommended value. Finally, an example of traction-separation law with dilation considering damage was proposed. Utilizing finite element method, interface pressure, mixed mode effect, unloading and reloading behavior, and effects of contact penalty stiffness on normal separation were investigated thoroughly.