Abstract: The multiphase tectonic events and long term karstification are responsible for the formation of the uneven fissure and pore space systems as main storage spaces of the Ordovician carbonate reservoirs in the Xayar uplift in Xinjiang. Following the deposition and diagenesis of the Ordovician carbonate sediments, there occurred the Caledonian-Indosinian-Yanshanian tectonic uplifting, exposure, erosion, karstification, leading to the appearance of the widespread weathering-type karstification. Four stages of karstification have been distinguished:middle and late Caledonian, early Hercynian, late Hercynian and Indosinian-Yanshanian, of which early and late Hercynian are considered to be most important stages of karstification. The karstification is believed to control the formation and distribution of the Ordovician carbonate reservoirs.