Three dimensional models of split rotary rings and split stationary rings established were numerically simulated by ANSYS.The effect of the joint face on the overall mechanical seal under different bolit pretension,medium pressure and spring specific pressure was analyzed,the tightness of joint face was studied.The simulated results show the stress distribution is uniform with real case,verifying the correctness of the FEM simulation method.Seal face deformations of split rotary rings and split stationary rings with screw pretensions under different working conditions present axisymmetric and continuous distributions,and the deformations are weakened effectively by the appropriate bolit pretension,the effect of joint face on seal ring are also reduced effectively.Bolit pretension is the key factor affecting the deformation of joint faces,with the increase of bolit pretension,the deformation is reduced effectively,and the tightness of joint faces is enhanced.