It's quite necessary to clarify the relationship between the various thread connections on the Christmas tree and the relevant instrument connections defined in API Spec 6A to solve the problem of roll-torque causing uneven loading for cone sealing and bending deformation for nipple of high pressure instrument installation for wellhead Christmas Tree. The 60° cone sealing required by API Spec 6A for high pressure instrument connections owns high sealing and low torque performance. It also isolates the corrosive substance from the pressure bearing thread and improves its application in high pressure and high corrosion environment. A convenient and feasible selection and installation solution is introduced in this paper based on the standard, actual filed conditions, cost of investment and experience and lessons. The optimized solution presented in the paper is instructive for relevant project engineering and lays a firm foundation for the standard installation of instruments of Christmas tree equipment.