With national economy rapidly development, mechanical vibration happening in high-speed rotating machinery could affect or restrict the normal work of system, and these will cause some loss of production or life. Vibration control of machinery became a hot topic in recent years. Usually, the plus damping method is used to suppress mechanical vibration in engineering practice. A kind of self-sensing eddy current damper which can be used in restraining machinery vibration of rotating components is studied in this paper. Electric eddy current testing method with double-wire transmission type is adopted in designing self-sensing damper structure. The working principle of it is analyzed based on the eddy current effect and electromagnetic theory. Detection model and actuation model of the damper are established using impedance analysis theory and electromagnetic theory. The characteristics of the damper are analyzed by an instance simulation, and the mutual influence between the vibration displacement and the input and output of damper is discussed. Finally, the experimental results show that the theoretic modeling is correct and the damper has self-sensing function.