Luanchuan polymetallic mineralization area is located in a large fracture belt containing 4 large fractures across with the main and secondary structures well developed. The borehole collapsing and difficult coring come into being because of loose and broken formations such as fracture alteration belt and argillaceous sand gravel. High requirement of bit is necessary for frequent soft and hard alternant formation. The borehole structure is complicated and construction efficiency is difficult to be improved. Good results were got by improving the property of washing fluid, using JS122 wire-line coring tool and searching for bit adaptability for formation.