Abstract: Aimed at the discussion that the paleo-environment was or not influenced by seawater when Shanxi Formation was deposited,microelement testing is analyzed.And the result shows that the water in paleo-environment mainly was freshwater,but periodly influenced by seawater.Applied with field outcrop and core description,combining with sedimentary cycle,the character of lithology and electromotive curve,sedimentary structure etc,the front delta in meandering delta of Shanxi Formation are identified in study area,in which subaqueous distributary channels were developed widely and was the main sand body for gas accumulation.Furthermore,sub-aqueous distributary channel,inter-distributary bay,inter-distributary swamp etc are main micro-facies in front delta.The sedimentary microfacies of Shan₂³ in plane are discussed.