Abstract: China costs more than ten billion US dollars yearly to import oil to cope with increasing domestic demands. The consistently increasing huge cost and the stability of petroleum provision oversea promote government and the top three national oil companies to pay more attention on the possibility of using more oil oversea and utilizing oversea resources more efficiently. Referring to the experiences from Petronas and BP, looking back and forward to the oversea business in the upstream of the top three Chinese oil companies is necessary on the sustainable development for Chinese petroleum industry.