Ordovician carbonate hydrocarbon reservoir spaces are mainly corroded cavities in the Ordos basin. The dissolve freckle of single chip as the research object, about 300 rock chips of more than 100 drilling wells are observed. The results show that the filling degree of cavity is distinctly zoning. The cavities in the eastern and western area are completely filled and pores disappear. But, the cavities in the central area are partly filled, there are a lot of pores remained which provide advantageous spaces for oil and gas reservoirs. Holes fillings are mainly dolomite, calcite, a small amounts of quartz, gypsum and kaolinite. Dolomite and calcite are markedly divisional, in eastern area calcite is mainly holes fillings, and in central area dolomite is as primary holes fillings. Based on the Ordovician residual thickness graphs and cumulative thickness graphs which are from the top of Ordovician to different layers, the ancient tectonic faces of the top of Ordovician in different periods can be recovered. The analysis suggest that the regionalization of hole filling degree and the fillings type is mainly controlled by the ancient tectonic patterns. At that time, the central area is high and the earstern and western is low after Ordovician and before the Early—Middle Triassic. By using of fillings microscopic characteristics, carbon oxygen isotope, the elements(Fe, Mn, Sr) contents and hydrocarbons fluid inclusions, the comprehensive results show that the hole fillings formation can be obviously divided into two stages. The hydrocarbons fluid inclusions in late fillings have abnormal high temperatures and are affected by the deep thermal fluid flow. The study of the distribution laws of holes filling degree and the fillings type in the Ordos basin provides a important basis for zones optimization of Ordovician karst reservoirs and points out the direction of natural gas exploration.