The deep copper-gold deposit in GUI Shan contains super thick weathered and fractured zone, severe collapse was encountered during drilling, which led to the difficulties of pipe tripping and hole cleaning. Therefore, the solid-free polyvinyl alcohol drilling fluid was used to enhance the collapse prevention ability.The experiment indicated that the higher the amount of polyethylene, the higher the viscosity of the drilling fluid, and the stronger the ability of stabilizing the core without disintegration. However, there is no obvious water loss-control ability. The use of FT342 can significantly reduce the water loss, and has good lubrication. This drilling fluid was used in drilling through the broken carbonaceous shale and coal seam during the section of 714～834m of ZK141 borehole, the scaling on the inner wall of drill pipe was solved with a good effect of preventing collapse.