Abstract: The northern ma rgin a rea in Qa idam Basin has been explored for many years, where some oil and ga s fields such a s Lenghu,Nanbaxian and Mabei ,whose hydrocarbon source rocks are mainly Jurassic sources, were discovered.Through comprehensive analysis of petroleum geological conditions in this area,it is considered that the main control factors of Jurassic oil and gas reservoir-forming in northern Qaidam Basin might be fea tured by a s followings: a.The distribution of oil-gas phase state are controlled by the distribution of hydrocarbon source rocks, hydrocarbon evolution and hydroca rbon-generating center; b.Key time of oil-gas migration and accumula tion in northern ma rgin of Qaidam Basin is Later Eogene and Middle Neogene, the important structural factors that controlled oil-gas migration and accumulation a re the paleouplift developed in Yanshania n period and structural belts developed in Eogene;b.The large-scale regional unconformity face developed between Mesozoic and Cenozoic eras and regiona l permea ble sandstone distributed in Tertia ry offer the favorable condition for oil-gas la tera lmigration;d. Violent activity of main-controlled faults and their derived fa ults in Later Himalaya period is helpful for oil-ga s vertical migration.

Key words: northern margin area of Qaidam Ba sin, Jurassic;oil-ga s resources;main-controlled factors