The isotope composition of pedogenic carbonates in paleosols is an effective approach to quantitative reconstruction of atmospheric CO₂ partial pressure. Stable isotope analysis of pedogenic carbonates from the Late Cretaceous Tangbian Formation in the Xinjiang Basin of Jiangxi Province was conducted to understand the paleoclimatic conditions. The carbon isotope compositions range from -4.30‰ to -2.10‰ (PDB) with an average of -2.84‰, and the oxygen isotope compositions range from -6.62‰ to -1.14‰ (PDB) with an average of -3.62‰. The CO₂ partial pressure was calculated to be from 782 to 1 420 ppmv based on Cerling's formula with an average of 1 181 ppmv during the Campanian Stage (~75 Ma), which is about 2~4 times higher than that of the present-day level. Therefore, a marked high value of CO₂ partial pressure probably occurred during the late Campanian Stage, possibly reflecting the undulation of p_CO2 during the Late Cretaceous time.