Abstract: The strata in Yinshan Au-Cu lead-zinc multi-metal mine are mainly in form of phyllite.Due to the complex schistosity of phyllite and big occurrence change，the degree of borehole curvature is over norms in deep-hole drilling construction process，which seriously hampered the drilling quality.In order to effectively resolve this problem and improve the drilling quality and exploration results，a technical breakthrough is made，where pre-floating measures are adopted with better results.  

Key words: Dip angle in drill-hole, Pre-floating, Drilling