With the development of deep and ultra deep wells,the packer will withstand extremely complex working conditions such as high temperature,high pressure,and corrosion for a long time after being set.A sealing structure of the packer rubber cylinder was designed.The sealing structure selected different materials according to the functional characteristics to make the packer suitable for use in complex working conditions such as underground high temperature and high pressure.Based on the actual extreme working conditions underground,the setting and sealing tests were carried out for the designed packer,and the mechanical behavior of the rubber cylinder under given working conditions was analyzed using commercial software ABAQUS.The results show that the designed packer can work stably under 0.2 MN setting force,70 MPa sealing pressure and 204 ℃ temperature.The rubber stress level of the packer rubber sleeve remains well below the yield point of the material,ensuring the durability and reliability of the packer throughout its operation.The rubber cylinder can generate contact stress greater than 70 MPa pressure difference,ensuring that the packer can withstand 70 MPa pressure difference.