Abstract: The Ordovician Lianglitage formation in Zhonggu?15 well area of central Tarim basin is of reef?flat karst reservoir, but different from other areas in this basin in horizon. It is mainly distributed in grain limestone bank of reef?flat facies of the third member of Lianglitage formation, and then in algal?laminated cryptite in lime mud mound. The main reservoir spaces consist of vug, cave and fracture, belonging to low?porosity and low?permeability reservoir. In accordance with the data analysis of the thin?section, diagenesis texture and microelements, it is recognized that the reservoir formation is closely related to the reef?flat karst and late burial karst reconstruction in the period of the third member deposition