In order to improve the sealing effect of electro hydraulic servo swing motor,the finite element analysis software ADAINA was used to analyze the contact stress of the combination sealing composed of PTFE sealing and O ring with different sealing structure,pre compression and medium pressure.The quantitative relationship of the leakage rate and friction was deduced with the gap flow principle.The sealing structure and the pre compression fitted for the swing motor were selected and confirmed in considering the sealing leakage and friction.The friction coefficient of the PTFE was tested in the same medium pressure and different frequency by friction and wear testing machine in order to analyze the friction condition of the PTFE in different working frequency.The results show that this combination sealing can meet the dynamic performance requirements of the electro hydraulic servo swing motor.The O ring has good sealing effect in pre compression of 20%,and the star sealing element has better withstand voltage ability,which is more suitable for the sealing of electro hydraulic servo swing motor.The friction coefficient of PTFE is decreased with the increase of operating frequency,it is suitable for working under the condition of high frequency.