Abstract: The KOP in the short radius sidetracking horizontal well in Tahe Oilfield is usually located below 5300m,this makes horizontal drilling very difficult.By illustrating the technical difficulties of drilling short radius sidetracking horizontal well,combining with the design and field drilling of well TK405CH,the successful practices on downhole tool and instrument modification,suitable techniques and technologies selection were presented.The following technical difficulties such as trajectory control technology,mechanics analysis and friction/torque analysis of drill pipe in high building rate in the short radius horizontal well were also discussed,and some corresponding solutions were proposed,which were field proven effective.