Karst porous fractured reservoirs are found in Ordovician limestones of Qilian sea area in northwestern Ordos basin and have better gas-bearing ability, showing that karst porous fractured reservoirs are a new form for carbonatite’s natural gas exploration. Through the analysis of geologic setting of paleokarst cavity’s development, the characteristics of paleokarst porous fractured reservoir based on the well drilling, logging data and seismic response are analyzed and two types of reservoirs are classified. Based on the seismic identifying pattern of wells, it is concluded that the target areas of Kelimoli Formation karst porous fractures are planar distributed, forming better reservoir-forming assemblage with Ordovician source rocks, which are the important areas for the future’s natural gas exploration.10.5pt" lang=EN-US>