With the fluidfilm between the faces of the static and dynamic of outside spiral groove mechanical seal as the study object, the periodic three dimensional (3D) finite element model (FEM) was set up. The flow field dynamic characteristics were simulated unmercially by Fluent of Computational Fluid Dynamics (CFD) software, then the pressure distribution law and the opening force of the fluidfilm were obtained, the results were compared with analytical an calculation ones. The results show the simulation ones are in good agreement with analytic ones, thus the method of simulating is reasonable. Then based on this model, the effectting law was numerical simulated of operating parameters (rotating speed, pressure difference, and viscosity) and spiral groove parameters (as helix angle，depth ) on the leakage，friction torque，dynamic pressure characteristics and opening force of the fluidfilm, which studies provide a useful reference for the design of spiral groove mechanical seal.