Abstract: This paper analyzes the adverse geological phenomena in the Diaokou lobe of the Yellow River Delta for their formation history and stratigraphic sequence, based on the data from boreholes, sub-bottom profiles and previous researches. The adverse geological phenomena observed include land subsidence and uneven settlement, soil liquefaction, weak strata and diapirs, landslides, and differential erosion. Discussed are the formation mechanisms, features and risk of these adverse geological phenomena. These phenomena observed in the Diaokou lobe also occur in the present Yellow River delta since they are similar in stratigraphic sequences. The Chengdao Oilfield is located on the Diaokou lobe. High attention should be paid to these phenomena in geotechnical engineering work to avoid geological disasters.