C-O isotopic analysis of carbonate sampled from the Mesoproterozoic Gaoyuzhuang Formation in the Kuancheng Area, Hebei Province, demonstrates that the original components of the carbonate have been well preserved. δ13C and δ18O ranges from -5.03‰~0.07‰ and -9.92‰~-4.12‰, respectively, with averages of -0.90‰ and -6.58‰, all of which are lower than those of Jixian section in Tianjin and Ming Tombs in Beijing by previous workers. The results show that the δ13C value in the studying area is mainly influenced by the oxidation degree and the buried rate of organic carbon, as well as the quantity of the blue green microalgae.