Abstract: The epidiagenesis undergone in conbonate rocks of lower SHA-1 in Gikou depression of Dagang oil field includes dolomitization, dedolomitization, cementation, dissolution, compaction, pressolution, recrystallization and fracturing etc. Furthermore, the dissolution, dedolomitization,recrystallization and fracturing is faborable for the reservoir; espically, the dissolution improved greatly the reservoir properties, while dolomititation, later-cementation, compaction, and pressoluticn are unfavorable to the reservoir, It is shown that the good, good-moderate, moderate and moderate-poor reservoirs are developed respectively in Wangxizhuang, western Gikou depression, Zhougingzhuang and Kouchen areas.