A scaling relation is presented after a concrete analysis of the properties of topology and mercury porosimetry processes for porous media. Then a new method and the corresponding procedure using the above scaling relation are set up in order to obtain the surface fractal dimensions of porous media from the experimental data of mercury intrusion. In contrast with the existing methods of this kind exhibited in literature, the results simulated by means of the method here for several kinds of porous media conform to the prerequisite for being surface fractals, which means the surface fractal dimensions should be in the very range : 2 less-than-or-equal-to D < 3. At the same time, this method gives almost the same surface fractal dimensions as the adsorption method. The evidence deduced from the results and analyses of this paper shows that this method may be a promising one to decide or at least estimate the surface fractal dimension for porous media.