Abstract: To overcome the scale dependence of the contact model based on statistical parameters and the shortcoming that the initial profile of existing fractal contact models depends on contact area or sampling length, a new fractal contact model for rough surface was established based on fractal dimension D, fractal roughness G and the base size l of the largest asperity. The asperity deformation mechanism and the relationship between the true contact area and contact load were explored. The variation law of porosity of the contact interface and real contact area under different surface topographies and normal forces were discussed. The maximum deformation \delta that characterizes the deformation to compact the profile pores for different morphology interfaces was also given. The results show that the asperity deformation initiates from elastic deformation to elastoplastic deformation, and then transforms into full plastic deformation with the increase of average contact pressure p_\rm m. The initial porosity \phi_0 of the contact interface increases with increasing D and then the maximum deformation also increases. The porosity \phi decreases with the increase of contact pressure p_c, and rapidly decreases with increasing D and decreasing G until it becomes zero. The effect of the increase of G on the increase of the real contact area can be ignored when D is small. However, when D is large, an obvious increase of the real contact area can be found as G increase. The research could provide a theoretical basis for the lubrication and sealing design of friction pairs.