Abstract: Settling tank is one of the most important equipments during the process of crude oil dehydration, simple in operation, strong in processing ability and suitable for oil with various physical properties. To find out the regulation pattern and methods under abnormal working conditions, proceeding from the structure and working principle of the settling tank, tracking the operating process of settling tank in Xi-Ⅰ Complex Station in Changqing Oilfield is carried out. Based on actual field experiences, this paper comprehensively analyzes the effects of temperature, inlet of liquid volume, additive dosage and settling time on settlement, and the reason why abnormal operation takes place based on control parameters of settling tank. Then, the regulation measures for settling tank under abnormal operations are proposed to avoid blind regulation, providing a feasible solution to the regulation of settling tank under abnormal operations.