While the fact that abrasion leads to change of surface topography is taken into consideration, the influence of spring pressure both on leakage rate and on friction characteristic of contacting mechanical seals are investigated by fractal theory. Several GY-70 type mechanical seals are tested. Both theoretic analysis and test results indicate that the friction will be more serious because lubrication medium between two end faces reduces as spring pressure increases, though the increase of the spring pressure may not be enough to change the face friction state of mechanical seal. There is an optimum spring pressure for mechanical seal operation. Under different operating conditions, identical type mechanical seals may possess different spring pressure. Appropriate selection of spring pressure is key to the mechanical seal operation under the best condition.