Aiming at the demanding requirements of sealing performance in ultra⁃deep oil and gas wells, a double main sealing structure consisting of conical surface to conical surface and cylindrical surface to spherical surface was designed based on the special thread sealing mechanism. Using numerical simulation method, the changes of contact stress and the contact length of the sealing surface under the four conditions of tensile, compression, tension and internal pressure, tension and internal and external pressures were analyzed. The sealing performance of threaded joints under the ultimate load was studied, and the change rule of sealing capacity with different loads was obtained. The full⁃scale test results show that the sealing performance of the double main seal premium threaded joint meets the application requirements.