Abstract: This paper describes the specific structure of a double shoulder connection with a metal to metal seal structure. The connection's make-up torque is consisted of four parts friction torque, which come from inner, outer shoulder surface, sealing surface and thread contact surface. Due to the change of bearing structure, API recommended torque calculation formula is no longer suitable for gas sealing joint. In this paper, a conical interference fit model and stress-strain model are used to establish the corresponding torque calculation formula, and the reliability of the theoretical calculation is verified by finite element method. The theoretical calculation, finite element simulation and full size make-up test are combined to determine the optimal torque of the joint, which provides reference for manufactures and fields to determine the optimum make-up torque range of gas sealing joint.