Abstract: Based on the research of formation condition and distribution law of hydrocarbon accumulation in Mianyang sag, its major control factors are analyzed. The results indicate that the general pattern of hydrocarbon distribution is controlled by hydrocarbon generating center of Baimiao syncline, reservoir formation is affected by reservoir qual- ity, and the faults which link up the source rocks are favorable for hydrocarbon migration and accumulation. As the formation and development of structural traps and its hydrocarbon filling are controlled by Himalayan movements in middle Eocene and Miocene, the specific distribution of hydrocarbon reservoir is determined by trap development belts. Therefore, source rocks, reservoir quality, oil source faults and structural belts are considered to be the main control factors of hydrocarbon accumulation in Mianyang Sag. It is also considered the most favorable targets for exploration are Zhoujiawan nosing belts in Yangliwei - chahekou play and Kaixiantai area in Pengchang - baimiao play.