A 120-m-long core (33°54'N;102°33'E;altitude 3 400m) has been drilled at the center of Zoige Basin of the northeastern Tibetan Plateau. The sediment core RH reaches back to 826kaB. P. according to ¹⁴C ages and paleomaganetic stratigraghy. By analyzing environmental proxies for spore-pollen, ostrode.diatom, fosvsil pigments, hydrogen index, the δ¹³C values of organic matter and so on, the sequences of climatic evolution in this region over the past 820ka have been rebuilt. Compared organic matter δ¹³C with other proxies from the core RH.we found that the changes in δ¹³C of organic matter correspond well with that of other climatic proxies in the core RH, and can be mainly relative with the record from the deep-sea oxygen isotope, suggesting that the organic matter Sl3C in the core RH is a sensitive environmental proxy. By using maximum entropy method, in this paper, we present the revsults of the frequency rhythms recorded in the δ¹³C proxy in the sediment core RH over the past 800ka. The results showed that:(1) 0-800ka, existing quisc-periods of 80ka, 60ka, 41ka and 20ka, in which the periods of 41ka and 20ka are very close to those predicted by the Milankovitch theory. (2) 0-480ka.power spectra showed a dominant peak near lOOka and smaller peaks at the orbital periodicities of 41ka and 20ka; (3) 480-800ka B. P., discovering the dominant periods of 115ka, 33ka and 16ka, while the periods of 100ka, 41ka predicted by the Millankovitch theory vanished. All the results demonstrated that during 0-480ka B. P. the climatic changes in the region were controlled by orbital forcing, and for the past 480-800ka B. P. the periodicities had greatly regional characteristics affected by the regional constructal actions. Therefore.in this period.the climatic changes are not only influenced by orbital forcing but strongly controlled by the constructal actions.