The rocks in Mo-Au ore section of Nanping mining area are broken into blocks and clastic rocks of different sizes by geological stress with joint fissure development, loose cementing; in this case, the collapsing is easy to cause knock-on effect and would be out of control. Big particle cuttings containing breccia would block borehole with washing fluid in uphole circulation. Study was made on the selection of washing fluid and drilling technology, by the practice of borehole control on ZK557 and ZK477, effective methods to treat such formation were successfully found out.