Abstract: The Bachu-Mageti area in Tarim basin underwent multistage tectonic movements,forming a certain number of unconformities，which were closely related to formation of the oil-gas reservoirs. Up to now，Niaoshan gas reservoir and Hetian gas field have been found and confimned their relationship with the unconformities. The study showed that there exist six unconformities in total development from Sinian to Quaternary. The important is the tops of Ordovician and Tertiary and the bottom of Pliocene series. According to the properties and relations to hydrocarbons, the unconformity can be classified into four types which could control the types and distribution of oil reservoirs to a certain extent.

Key words: Tarim basin, Bachu, Mageti, unconformity, characteristics, hydrocarbon, relation