The Ordovician sequence stratigraphic framework has been erected in this paper on the basis of the investigation of outcrop sequence stratigraphy and sedimentology along three sections in Keping area, northwest Tarim Basin. The Ordovician strata can be divided into six third-grade sequences. Correlations shows all these six sequences can be recognized in the Sishichang section, while only the lower three ones are developed in the Subashi and Tongusibulong section. Carbonate magnetic susceptibility is negatively related to the relative sea level change, while its curve can reflect the sequence boundaries and system tracts of the third-grade sequences respectively. The results obtained by the authors indicate that carbonate magnetic susceptibility can be used as a quantitative index to assist the division of stratigraphic sequence.