Abstract: Sandaozhuang molybdenum-tungsten ore district in Henan has complex geological conditions and fractured strata, leading to some exploration difficulties.Hollow-through DTH hammer reverse circulation drilling technology for continuous coring is used in the exploration and has achieved good effect.This method has the advantages of high drilling efficiency, high rate of coring and good drilling quality, effectively solving the drilling problem in fractured strata.In view of the challenges of extremely serious leakage and poor core integrity in complex strata drilling, improvement is made on the reverse circulating drill bit.The technical features and its practical application of this process are described in detail in the paper.

Key words: Hollow-through DTH, Complex strata, reserve circulation bit, inner jet hole