Abstract: Since 1955, the petroleum exploration of the northern margin of Qaidam basin has carried out for over 40 years, but no large-scale reserves have been found, except for a middle-sized field named Nanbaxian by the end of 1990s. The oil resources in this area amount to 10x10⁸t, but incremental reserves are seldom discovered, with degree of conversion of oil resources by 3.2%. The reasons for it are as follows: Altun shove fault's destructive effect on petroleum migration in the northem margin; absence of good regional cap rocks; not enough fundamental study work on the Jurassic, and uncontinuity of related prospecting eforts. AIll these add the difficulty for exploration of it. It is suggested that the further exploratory effort should focus on buried or subtle structure and lithologic trap in swell slope, paying attention to restudy of Saishiten piedmont overthrust nappe.

Key words: northern margin, Qaidam basin, Jurassic, petroleum prospect