This paper presents numerical modelling (on the spread, transport and ageing of the oil slick from an accidental oil spill in the center of Jiazhou Bay under NE,SW, SE and SW winds) showing that when wind speed is greater than 5m/s, winds exert greater effect than tides on the oil slick; and that if wind changas its direction from N to S during the time of the oil spill, the oil slick will spread to most parts of the east coast of Qingdao.