94 marine carbonate samples were collected from the sedimentary section of Cambrian in Xiushan of Chongqing, the Upper Yangtze Platform, Southwest China. Samples for strontium isotopic analysis were selected by way of the test of cathodoluminescence, observation of thin sections, and analysis of Sr and Mn. The Mn/Sr ratios of all samples presented in this paper are less than 2, and the cathodoluminescence is dull, but the samples from the Cambrian underwent diagenetic alteration to a certain degree, and the plotted points of the thicknesses and 87Sr/86Sr ratios are somewhat discrete. The strontium isotope evolution curve drawn using the data with relatively low 87Sr/86Sr ratios are consistent with other curves based on samples from different areas of the world, supporting the notion of global consistency of strontium isotope composition of marine carbonates. The strontium isotope variations through time reflect the relative importance of global events, and will become a potential useful tool for intrabasinal and interbasinal correlations. According to this fundamental principle, the authors have dated some key points of the Xiushan Cambrian section. The age of the point with an accumulating thickness of 1340 m from the base of the Cambrian System is 503-509 Ma, and that for the point of 1950 m is 496-498 Ma, which should be valuable for determining the boundaries of Middle/Upper Cambrian and Lower/Middle Cambrian.