Abstract: Reaming while drilling can enlarge diameter of lower borehole effectively, and it is very significant for optimizing wellbore configuration, improving drilling efficiency and completion quality, and decreasing subsequent operating risks. While drilling in straight hole, it could be regarded as a packing centralizer and it could prevent from slanting, however, reaming while drilling in oriented section would alternate the angle buildup of common buildup assembly, so further research on its applicability in oriented section was needed. Taking a suit of common buildup assembly as an example, initial buildup rate and buildup rate of direct reaming and reaming while drilling were calculated, and found it influence the buildup rate of original downhole assembly a lot. To obtain good angle buildup effects, BHA parameters（bend angle of helicoid hydraulic motor, outside diameter of upper centralizer, the distance between upper centralizer and drill bit, and so on） was adjusted, and it meant that reaming while drilling could be implemented in accordance with the established requirements.