Abstract: The carbonate platform margins of Lower Paleozoic are an oil?gas enriched region. The seismic, logging, core and outcrop data from this area reveal that the structural types of the platform margins of Middle-Lower Ordovician in different areas in Tarim basin are big different. Tabei area (the northern Tarim) occurs in steep retrogradation rimmed margin type, Tazhong area (the central Tarim) in steep aggradation rimmed margin type, Taxi’nan area (the southwestern Tarim) and Awati area in weak aggradation?progradation ramp types, and Ta’nan are (the southern Tarim) is in weak aggradation?progradation steep?ramp type, with inheritance inter?platform slope facies. The comprehensive study of structure, deposition, paleo?environment and diagenesis, shows that:1) Tabei and Tazhong areas were located in the windward side with steep slope gradient of margins in Early-Middle Ordovician, and Taxi’nan and Awati areas were located in the leeward side with ramp slope gradient;2) Tectonic subsidence rate from platform to basin in Tabei area was fast when the synsedimentary occurred, the structures of platform margin were on style of retrogradation; while Tazhong area changed slowly, the structures on style of aggradation. It is suggested that the structures of platform margins are affected by paleoclimate and tectonic subsidence rate. The comparisons of carbonate platform margins are in favor of the reconstruction of lithofacies palaeogeography and the prediction of vertical?lateral distribution of favorable shoal reservoirs, and it is meaningful for petroleum exploration extension from platform margins to inner platform of Lower-Middle Ordovician in Tarim basin