In order to reduce the drag and torque in directional well drilling and increase the ROP, according to the geological conditions and drilling difficulties, a regression calculation model of borehole trajectory and rock drillability was established. By the optimization of 5-section trajectory sections, the optimal hole curvature 2.85°～3°/30m and maximum well angle 30°were determined, the intermediate casing was put down to sadi layer 8～15m to ensure the completion of S-shaped directional well. As the result, the friction coefficient in the open hole is reduced from 0.52 to 0.35 and casing internal friction coefficient from 0.35 to 0.28. The quick wearing of conventional PDC bit and low ROP of cone bit are solved by optimization test on KM533 composite bit in RUS soft and hard interlayer. Based on the technical research and application, the actual top driven torque of Rumaila S-shaped directional well is lowered by more than 30%, the mumber of used bits is reduced by 2.7 and the drilling period is decreased by 18.58d.