Abstract: According to the features of carbonate fractured-vuggy reservoirs in Ordovician in the Tahe Oilfield and the well-controlling problems such as killing methods, completion testing string designs and wellhead-dressing methods, new techniques were innovated for wellhead-dressing and new tools for well-controlling were introduced. In view of the reservoir size and fluid properties of Ordovician, a new method suitable for killing the Ordovician complex reservoirs in the Tahe Oilfield was proposed, and a conventional completion testing string system was designed, which could deal with the Ordovician reservoirs with different oil properties and different gas/oil ratios.