Abstract: Groundwater system of Cretaceous system of Ordos basin in terms of system of water-bearing stratum of groundwater was divided and analy sesed. Because Bao'an group of lower Cretaceous system is formed of clastic rock of a set of land facies,which rock is complicated,made up of sand stone,flour sand rock and mudstone. And these stratum frequently replace,repeat apile of multilevel layer of forms structu reput,determine Cretaceous system of Ordos basin which groundwater flowau to matically is multilevel groundwater system of structure. And It determines the groundwater system is multilevel stratum,confined and relatively close between stratum and stratum. According to depositing gyration and quality of aquifer material,the Cretaceous system groundwater system is divided in to Luohandong aquiferous group,Huanhe aquiferous group and Luohe aquiferous group from up to low with in the range of the whole basin. The author has analyzed the three aquiferous groups separately. Based on above these, Huanhe aquiferous group and Luohe aquiferous group,which distribu terange wide,aquifer stratum thickly,natural resou rce abundantly,are the main aquiferous stratums to supply water of the meaning. Luohandong aquiferous group distributea slimited,thickness widely different,water quality changing heavily,besides east area of Gansu Province,value of supply water is relativelylittle in most areas.