In slim hole sidetracking drilling,88. 9 mm diameter direct type drill pipe can effectively reduce the pressure loss along the path and increase the rock carrying,also can transfer torque effectively,rotary drilling to improve drilling efficiency. In order to meet the actual needs,improving the carrying capacity of 88. 9 mm drill pipe joint in slim hole drilling,this paper presents a low tooth-double shoulder-special thread. By 3 D Finite Element analysis,the performance of thread connection were studied,including the stress in three-dimension under different loads and the limit torque under different axial tensile loads. And draw out the limit torque curve of the tool joint. Forming a quickly method to determine the tool joint limit torque under different tension. The research is of great significance for guiding the selection and optimization of the drill pipe joint,analyzing the limit load of the drill pipe joints and determining the the limit drill depth.