Northwest China in this paper refers to the broad region bounded by the Helan Mo untains and Liupan Mountains to the east, and by the Kunlun Mountains to the south. Based on the study of stratigraphy and petrology of outcrop and well sect ions, according to single factor analysis and comprehensive mapping method, vari ous single factor maps of the Lower, Middle and Upper Ordovician and lithofacie s palaeogeography maps of the Early, Middle and Late Ordovician in Northwest Chi na were compiled. These lithofacies palaeogeography maps possess three character istics, i.e. quantification, multirank and multitype. Quantification means that the determination of each palaeogeographic unit is based on quantitative single factor data and maps. This makes palaeogeography develop to the quantitative sta ge. Multirank means that palaeogeographic units are classified into three ranks or more than three ranks. For instance, lands and seas are the first rank. In the seas, the platforms, basins and slopes are defined and belong to the second rank. In platf orms, the banks and tidal flats are further drawn out and belong to the third ra nk. Multitype means that the palaeogeographic units, especially the 2nd and 3rd rank units, can be further divided into different types on the basis of their ro ck types. For instance, platforms can be divided into carbonate rock platforms, clastic rock platforms, volcanic rock platforms ,etc.;basins can be divided int o mudstone basins, siliceous rock basins, clastic rock basins, volcanic rock bas ins, flysch basins, etc.;and banks can be divided into sparry grain banks (pene banks, embryonic banks), and limemud grain banks (penebanks, embryonic banks). T he framework of lithofacies paleogeography of the Ordovician in Northwest China can be summerized as following: There were both lands and seas. In seas there w ere platforms and basins distributed alternately. In platforms there were banks and flats. Between platforms and basins there were slopes. In the Early Ordovici an, the Cambrian transgression continued and became larger. In the Middle Ordovi cian, the transgression reached to its climax. In the Late Ordovician, the regre ssion appeared, and the refore the transgression and regression cycle of the Cam brian and Ordovician in Northwest China was completed.