Abstract: According to a type of serviced hydrodynamic mechanical seal in reactor coolant pump, a three-dimensional multi-field coupling mathematic model for seal assembly was developed, taking the contact and fluid-solid coupling between seal components into consideration. Combined finite difference method with finite element method, a numerical iteration method was used to solve coupling problem. The deformation characteristics of end faces were studied under different high pressure conditions; meanwhile, the influences of seal pressure on seal were analyzed. Results show that radial convergent taper and circumferential waves were formed on seal end faces, respectively due to affection of seal rings macro-structure and the existence of deep hydropads. When seal pressure increased, both the radial taper and circumferential wave on seal end faces increased; and an increasing leakage rate and a decreasing friction coefficient between seal faces were shown. In order to form a larger wave under high pressure, it is suggested that the deep hydropads are machined on the soft seal rings.