Abstract: The strontium isotope characteristics of23carbonate samples of Lianglitage formation of Late Ordovician from Ma?2well in Maigaiti area of Tarim basin were analysed for the purpose of making sure the sea?level changes at this period. The results show that the ratio of 87Sr/86Sr ranges from0.70851to0.70901, with an average of 0.70874, which is higher than the ratio of global seawater strontium isotope in the same period, but more consistent with those from the same horizons in such areas as Keping, Bachu and Tazhong regions. On the basis of the ratio of 87Sr/86Sr, the strontium isotope evolution curve of Lianglitage formation in Maigaiti area is obtained, which is consistent with the global seawater strontium isotope evolution curve of the Late Ordovician, better coupled with Bachu, Laurentia and Baltica old?lands, and well reflects the sea?level variation in this period. This understanding is of great importance for the study of the sediment changes and structural evolution of Late Ordovician in the whole Tarim basin