Abstract: It was discovered by study on the chemical field of the Shahejie formation water in the Dongying Sag that the total dissolved solid (TDS) of formation water has explicit vertical zonality.The value of TDS is the highest in the Sha-4 Member,and reduces gradually upward. According to the feature that the Ca²⁺ and K⁺+Na⁺ contents in formation water get higher with the increasing of Cl^- concentration,it is suggested that the chemical components of formation water in this area come from the dissolution of subsoil rock salt.Among CaCl₂, NaHCO₃, MgCl₂ and Na₂SO₄ four water types,the specific gravity of NaHCO₃-typed water has inverse correlation relationship with the TDS of formation water.The characteristics of vertical and lateral TDS distribution show that the flow of formation water within the Dongying Sag is controlled by faults and sedimentary sand bodies.Formation water is a major component of basin fluid,and its revolution reflects the rules of hydrocarbon migration and accumulation in the basin.The flow styles of formation water provide a powerful evidence for the formation of "self-generation,self-accumulation" and "lower-generation,upper-accumulation" two patterns of hydrocarbon pools in the basin.