Abstract: A measurement system was designed to accurately determine the contact stiffness between two surfaces of dry friction damper,so as to separate the system stiffness from the contact stiffness.The influences of exciting force and initial normal load were investigated in detail.The curve of the tangential contact stiffness for variable normal preload was obtained by fitting the results according to the given condition.This research can test and improve the calculation models,laying a foundation for establishing a practical method for numerical simulation of contact stiffness.