Aimed at the poor reliability of motor bearing seal,a type of upstream pumping mechanical seals with bi-direction fir-tree grooves for electromechanical transmission high speed motor was presented.The steady-state Reynolds equation was solved by means of the finite element method and MATLAB programming,and the pressure distribution of the fluid between the seal faces of the upstream pumping mechanical seals with fir-tree grooves was obtained.The influence of the geometrical parameters such as groove depth ratio(the ratio of groove depth to film thickness),spiral angle and the ratio of groove and dam on the steady characteristics was analyzed.The results indicate that the upstream pumping mechanical seal has good dynamic pressure effect.With the increasing of groove depth ratio,the opening force,pumping capacity and liquid film stiffness are increased first and then decreased rapidly,while the friction coefficient is increased slowly.With the increasing of groovedam ratio,the opening force and pumping capacity,the friction coefficient are increased,and the stiffness is increased gradually and tends to be stable.The groove depth ratio and spiral angle have a greater influence on the steady-state characteristics of the mechanical seal than the groove-dam ratio.When the groove depth ratio is between 1.0 and 4.0,spiral angle is between 15° and 25°,the groove-dam ratio is between 1.5 and 2.5,the mechanical seal has good comprehensive performance.