Abstract: This paper describes the several key technologies in e xtended reach dr illing, e.g., friction reduction, hole cleaning and well stabilization. Through the analysis to the mechanisms of high friction, hole instability and poor clean out, it concludes that friction reduction is not depended on the drilling fluid property, optimization of trajectory design, BHA design, use of new tools only, but on hole stabilization condition and cleaning efficiency also. Further more, hole cleaning is closely connected with drilling fluid property and other drilli ng parameters, and hole stabilization is determined by the strong inhibition of drilling fluid, reliable drilling fluid density safety window, and well trajecto ry. It concluded that a comprehensive consideration of friction reduction, hole cleanout and hole stabilization is critical for the successful drilling of an ex tended reach well.