Abstract: Evaporite is well developed in the middle Shasi column of Shahejie Formation，Tertiary system in Dongying Depression，where the thickness of saliferous layers with mudstone exceeds 1000 m in the southern Shengtuo and central rift zone．Analysis of many samples and study on sedimentary system show that the lake basin was in an under-filling condition．A deep water evapofite formation model was established．The geochemical characteristics of dark gray mudstone and shale in evapofite layers record the sedimentary environment of salt lake．The high salt medium is beneficial to organic concentration and preservation．The gray mudstone and shale in middle Shasi column was a kind of high quality source rocks in Dongying Depression．