Abstract: OPEC is an international organization with the cartel characteristic, which coordinates and unifies the oil policies of its 13 members. The oil policy of OPEC has a great effect on the world oil market. According to the data of history and present condition, the evolution law for the oil policy of OPEC has been studied in this paper. Some conclusions have been gotten from the writer's research. First, According to the changing situations of the international oil market, the oil policy in its economic and political interests has been carried out by OPEC by means of oil price system and production allocation regulation. Second, formulation and implementation of the oil policy has passed the initiation period, active period, frustration period, mature period and wandering period. Different policies have been carried out in every period with noticeable results. Third, 5 aspects of oil policy transition are put forward in this paper, the transition from rigidity to flexibility, from singleness to diversification, from competition to collaboration, from high oil price to reasonable price, from disagreement for oil policy among the members of OPEC to coordination. The oil policy of OPEC will be reasonable and rational in the future, which benefits both the production countries and the consumer ones.