In this study, low temperature (room temperature, 400°C LT) and high temperature (400–900°C HT) of bulk organic carbon samples were dated from two loess and paleosol profiles. The results showed that radiocarbon (14C) dates of the LT were younger than HT fractions, indicating effect of younger contamination from overlying layers. The δ13C variation of the HT fraction appears to respond much more sensitively to climate change, and 14C ages of HT fraction can produce reasonable 14C ages from a younger layer, but it is very difficult to obtain reliable 14C ages from older layer as a result of uncomplete removal of young carbon.