This paper reports the results of determination of 87Sr/86Sr ratios of some Middle-Late Pro-terozoic and Early Cambrian carbonate rocks in China. The samples were collected from the standard sections of the Middle Proterozoic in Jixian and the Sinian-Early Cambrian in the East Yangtze Gorges respectively. The sample analyses were carried out in the isotopic geology laboratories in Australian National University and the Yichang Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences. The data obtained were corrected for the Rb blank and the radiogenic 87Sr from87Rb decay. Finally the initial 87Sr/86Sr ratio for the formation of the samples was given. The reference materials of NBS-987 and NBS-607 were used for monitoring the instrument condition and the analytical process. The precision of the measured 87Sr /86Sr ratio is better than 0. 03%.A brief discussion is also made on the obtained data.