To deal with the various risks of high pressure salt-gypsum layer salt contamination and leakage, blowout, collapse and drill pipe sticking in lower limestone formation of deep horizontal well in Iraq Missan oilfield, as well as to reduce drilling cost and improve drilling efficiency, the research and operation on deep horizontal well are carried out in well 64H. Based on the block operation experience, the deep horizontal well is designed as a 6-spud well structure, the high-density saturated compound salt drilling fluid technology is adopted for high-pressure salt-gypsum layer, and a series of directional well and liner cementing technologies are implemented in deep limestone formation, which solve the drilling technical difficulties in this block, improved the drilling safety and efficiency and created a new drilling record of deep horizontal wells in Missan oilfield.