Abstract: The noble gas isotope of 8 crude oil samples of the Qingxi oil field in the Qingxi depression and Yaerxia oil field in the Southern uplift in the Jiuxi basin was measured. He source of the crude oils was discussed. The　3He/4He(Rc)ratios of the crude oil noble gases from 4 wells in the Qingxi oil field, the 527 well and the 702 well in the Yaerxia oil field reach an order of 10-8,indicating a crust radioactive source. This shows that the overthrusts related to the Qingxi oil field and the 527 well and the 702 well in the Yaerxia oil field cut into the depth of the crust. The　3He/4He(Rc)ratios of the crude oil noble gases
from the 501 well and the 114 well in the Yaerxia oil field is up to an order of 10-7, showing the input of a minor amount of mantle-derived helium and the cutting depth of the overthrusts associated with the two wells into the mantle. The geothermal flow of the Jiuxi basin is lower than that of the basins of eastern China, displaying that the basin has weak tectonic activity.

Key words: Jiuxi Basin, crude oil noble gas, source, geothermal flow