Metallic gasket seals are widely used in pressure vessels and piping. The failure of sealing systems is mostly caused not by the strength of flanges or bolts but by the leakage of the connections. The contact area of sealing surface has a major influence on the leakage of the bolted flange connections. The contact model of sealing surfaces of the flange and the metallic gasket was established on the basis of the modified M-B model, and the relationship between the contact area and the compressive stress is obtained. It’s found that the bigger the compressive stress, the bigger the contact area. When the compressive stresses are identical, the bigger fractal dimension and the less scale coefficient, the bigger the contact area. These can be used in the evaluation of sealing behavior of metallic gaskets.