Abstract: In view of the characteristics of Tahe oilfield,such as limited sidetrack drilling hole size of well bore structure,small cementing annulus clearance,and complex formation pressure system,oblique editor window sidetrack directional drilling and reaming technology has been adopted.Combined with the expansion pipe and slim-hole horizontal well drilling technology,the application feasibility of the directional reaming while drilling technology in deep wells of Tahe oilfield has been verified.Under the condition of invariable size of casing size,the increased casing annulus clearance,enlarged the hole size and improved the well cementation quality provide favorable conditions for subsequent completion and production operations.