Oil price recently dropped below $80 per barrel, but OPEC hasn't yet limited production to maintain price. In view of ANBOUND research team, the current oil-price fall is a sign that world oil market is going to conduct structural adjustment, originated from the role shift of the US in energy market. In a period of falling oil price, the withdrawal of oil dollar and appreciation trend of the US dollar might together trigger "intermittent liquidity shortage" in world financial market.