Abstract: In the Middle Cambrian Awatage Formation of Tarim Basin occur thick strata of upper-tidal red dolostones.Geochemical research was performed and results show a obvious positive correlation between the CaO% contents and the MgO% contents of dolostones, which suggests a sedimentary genesis. The relatively low contents of U and Mo suggest that the red dolostones might have formed in an oxidized environment, coincident with the red color. The PAAS-normalized rare earth element characteristics show a MREE-enriched pattern, which may result from high contents of Fe2O3％. There is no general regularity in carbon isotope variation among the studied wells. The oxygen isotope analyisis of dolostones from wells Tacan 1, Fang 1, and Yaha 5 shows high δ18O values, ranging -7‰~-4.4‰, indicating an evaporated sedimentary genesis, while the oxygen isotope of dolostones from Yingmai 7 well shows a relatively lower δ18O values (-11.2‰~-10.2‰), indicating the hydrothermal alteration character during the diagenesis process.