This paper, based on Cartel and competition models, discusses OPEC’s oil production behavior during 1971 to 2008, combines with OPEC’s reserve/production ratio and idle capacity, and the production changes during descending 1980 to 1985 and ascending 1999 to 2008, concludes that OPEC’s has no competition, in general its production behavior trends to occupy markets. OPEC’s core members include Saudi Arabia, Kuwait, United Arab Emirates, Libya, Qatar, interim members Iran, Iraq, Venezuela, Nigeria, and marginal members Angola, Algeria, Ecuador. It’s production size is controlled in the core members and partial interim members. Through setting quota, OPEC can control the gross 〖JP3〗production, which can basically increase the oil price. Saudi Arabia, Iran and UAE as three major oil exporters are relatively low in their production accretion, which played a key role in oil rise during 1999 to 2008.