Abstract: In the present paper, tree rings of Pinus tabulaeformis were sampled in the Summer Villa Estate of Chengde City, and their δ13C values were measured using a MAT-252 isotope ratio mass spectrometer, in order to reveal the historical changes of atmospheric CO2 in North China. The results show that, since 1810, the δ13C values in the tree rings of P. tabulaeformis have decreased by 0.839‰ with a range of 0. 682‰～1.120‰ ,indicating that the concentration of atmospheric CO2 has increased. There was a good linear correlation between the values of tree ring δ13C and the historical global atmospheric CO2 concentration (r = – 0.5609, p<0.01). By applying the formula of tree ring δ13C with concentration of atmospheric CO2, we estimated that CO2 concentration in North China has increased from 278.4 μmol·mol-1 in the preindustrialization to 340 μmol·mol-1 at present.