Abstract: The use of ?88.9 mm drilling tool in slim hole horizontal well in Sulige Oilfield has the problem of small flow rate, small torque and high pressure drop, causing the screw to be short of power when drilling the horizontal section, hence affecting the ROP and efficiency of horizontal well in Sulige Oilfield. The torque resistance of drillpipe body was calculated as per API REG 7G standard and the relation between connection size and torque performance was analyzed by finite element software, and the use of double-shoulder connection was proposed according to the requirement of special well drilling parameters for API tool connection, so the technical difficulty was solved that the ?101.6 mm drilling tool could not be used in ?177.8 mm intermediate casing while drilling the horizontal well in Sulige Oilfield, realizing large flow rate, high pump pressure and low circulation pressure loss during drilling and also satisfying the drilling of slim hole horizontal well in Sulige Oilfield.