Abstract: There might be two major stages in dolomite distribution throughout geologic history of Tarim basin,that is, Mesozoic and Early Paleozoic, The dolomite of Cambrian-Ordovician could be clasified into seven types by its structures. The following big differences display its variations in origin, such as carbon and oxygen isotope value, trace element content and inclusion homogenization temperature range. Based on lithology, carbon and oxygen isotope value, trace element content and diagenetic temperature, it can also be classified as penecontemporaneous dolomite,shallow buried dolomite and deep buried dolomite.

Key words: Tarim basin, Early Ordovician, Dolomite, Orgin, Carbon isotope, Oxygen isotope, Trace element, Diagenetic evolution