Abstract: Aiming at the formation characteristics and directional drilling difficulties in a mining area of Tarim basin, we have selected high temperature-resistant mixing materials with good rheological and mechanical properties to conduct experimental study on drilling fluid formulation by orthogonal experimental design method. The drilling mud system MV-CMC-80A51-NPAN with heat resistance of 100℃ and non-dispersed low solid polymer has been optimized. This mud has stable performance. Moreover, the mud has a high temperature resistance, low fluid loss, thin and dense mud skin, good shear dilution performance and low cost. It plays an important role for smooth directional drilling in hard fractured complex rocks to reach the target.