Abstract: Research on salt structures has important meaning to the exploration of oil and gas in the salt-bearing basin,it becomes one of the hottest topics of tectonic research and exploration for oil and gas.The major idea of this article is to discuss the evolution of salt structures and their control on oil and gas reservoirs in S block of Pre-Caspian basin,by way of analyzing the structural features in inter-salt strata.Based on the investigation of 2-D seismic profile of S block,the inter-salt strata can be divided into 2types:limb rotation growth strata and lateral pierced strata.The lateral pieced strata were formed around pierced salt dome during the P2-T1 period;the limb rotation growth strata were formed around unpierced salt dome during the T1-T3 period.Differences between these two types of inter-salt strata indicate their different paleostructural altitude,therefore the strata around the unpierced salt dome have more hydrocarbon accumulation potential than those around the pierced salt dome.