Abstract: Gaskets are often used to adjust the clearance during the installation of ship isolation systems， since the system may suffer from geometric dimension deviation. It has been also verified that the surface process quality of gaskets is closely related to its normal contact stiffness. In this paper，the exact relation is investigated between the normal contact stiffness of gasket surfaces and the gasket material properties as well as the fractal parameters，based on the fractal theory. A new method to estimate the normal contact stiffness is then proposed. The numerical results show that the contact stiffness increases as the value of surface roughness decreases or when the adhesion rate increases. Particularly，the adhesion rate plays a more important role when determining the contact stiffness. However，if the adhesion rate is fixed，little changes can be observed in the contact stiffness when Ra 3 6.3 μm ，while the change becomes relatively significant when Ra ￡ 6.3 μm . Thus，a balanced value of Ra = 6.3 μm is suggested for the practical surface roughness，considering the cost of surface processing and the effects of the contact stiffness on the overall system performance.