Abstract: There is an important relationship between the hydrochemical features of local water and oil accumulation.On the basis of the analysis of local water hydrochemical features and geological data of Dongying Sag, the planar division and vertical zo nation of paleogene local water was revealed.The lo cal water hydrochemical feature is controlled by later compaction and drainage, foreign fluid and fault activity except the primary sedimentary environment and climate condition.The dehydration and consumption of water because of mineralogic changing during diagenetic process are also important influencing factors.