In order to investigate the effect of sealing differential pressure and clearance on packing rubber of the packer,Von Mises stress distribution of packing rubber,the contact stress distribution between packing rubber and the casing wall,and the deformation of the packing rubber under different pressure and clearance were analyzed based on the finite element software.The results show that,with the increasing of sealing differential pressure,Von Mises stress value of packing rubber’s upper part is constantly increased,which may lead to the failure of packing rubber,but the contact stress between packing rubber and the casing wall is increased and sealing ability of packing rubber is improved.With the increasing of sealing clearance,Von Mises stress value of packing rubber’s upper part is constantly increased,the possibility of packing rubber shearing failure is also increased,and the contact stress between packing rubber and the casing wall is decreased which causes the decrease of sealing ability of packing rubber.A worm shaped antiextrusion ring was designed and its effect on the sealing performance of packing rubber was analyzed.The results show worm shaped protection rings can effectively prevent packing rubber protruding,the packing rubber has more uniform stress distribution and higher contact stress between packing rubber and the casing wall,so the sealing ability of packing rubber is improved.