Abstract: The free radical concentration (Ng) of kerogen is a valid index to study thermal maturation of organic matter and paleotemperature of sedimentary basin. A standard curve map was established to estimate paleothermal gradients based on the relationship between Ng and buried depth of kerogen samples from the Cenozoic basin. The paleo-geothermal gradients of well MC1, the Tarim basin and well LR16, the Liaohe basin were estimated by using the stardard curve. It gived a new way to study paleo-temperature in an area where vitrinite grain can not be found and apatite fission track analysis can not work because of lack of a patlte.