Abstract: With the wide applications of the logging technologies of the ultra-deep well, the horizontal well, the directional well, the extended-reach well and the highly-deviated well in the petroleum drilling engineering, the premature failure of the drill pipe joint caused by underground complex working conditions becomes increasingly a prominent issue, and it results in the increase of the drilling period and the drilling cost, as well as the reduction of the drilling efficiency. In recent years, the drill pipe joint was extensively studied, mainly focusing on the 2D axisymmetric model, with a few on the 3D mechanical model, but without consideration of the influence of the angle of thread and the bending of the hole at the same time. The ultimate bearing capacity of the drill pipe joint was not well studied. In this paper, a 3D numerical simulation model of the drill pipe joint and a model to convert the borehole curvature to the loading moment are established based on the principle of the virtual work, the von Mises yield criterion and the nonlinear contact theory, taking account of the influence of the angle of thread and the bending of the hole at the same time. The make-up property of the drill pipe joint is studied, as well as the influences of the borehole curvature on the connection strength and the sealing property of the drill pipe joint, and the ultimate working pull and the ultimate working torque of the drill pipe joint are calculated with consideration of the preload, the bending load and the dynamic load safety factor. It is shown that the make-up torque can provide a certain initial contact pressure to ensure the connection strength and the sealing property of the drill pipe joint in the process of the downhole operation. The borehole curvature has a great influence on the connection strength and the sealing property of the drill pipe joint in the process of the downhole operation. The connection strength and the sealing property of the drill pipe joint will be much affected under some common operating conditions. In consideration of the random vibration and the shock of service, the drill pipe joint used for the common ultra-deep well, the horizontal well, the directional well, the extended-reach well and the highly deviated well should be designed and selected with due consideration of the influence of the borehole curvature. For each kind of drill pipe joint to be designed, the accurate numerical calculation of the ultimate working pull and the ultimate working torque should be conducted for the corresponding borehole curvature and the axial tensile load to ensure safety.