Abstract: Based on the thin section analysis, fluid inclusion summarizing and microthermometry for more than 70 pieces of samples obtained from more than 10 wells in the Jiangjiadian area of Linnan sag, the paper reveals that the Esx3 reservoir of Shahejie formation underwent multi periods of acid-base fluid evolution and hydrocarbon charging during its burial process: 43.7×106 a — 37.0×106 a ago, the formation fluid was weakly alkaline, the diagenesis was dominated by compaction and a few early pyrites occurred; 37.0×106 a— 28.2×106 a ago, the thermal evolution of organic matter led to the acidity of formation fluid, and feldspar dissolution and the first phase of quartz overgrowth took place; 28.2×106 a—24.6×106 a ago, decarboxylation of organic acid as well as dehydration of gypsum bed in the lower Sha-4 member occurred，thus the formation water became alkaline, and carbonate cementation and quartz dissolution were noted; 24.6×106 a—14.0×106 a ago, thermal evolution of organic matter made the formation water acidic and the second phase of acid dissolution and quartz overgrowth began; 14.0×106 a—2.8×106 a ago, re-evolution and hydrocarbon generation happened to the source rocks, which made the formation water continuously acidic; since 2.8×106 a ago till now, the formation water was acidic and a few late pyrite cements were found