Twenty-two rainwater samples from Guiyang city, southwestern China, have been analyzed for their chemical compositions and 87Sr / 86Sr ratios, with a main purpose to get a better understanding of the general features of rainwater in Guiyang city and their correspondences to human activities. The rainwaters studied are almost acidic (pH = 4.53) and show big changes in major ion composition. Ca 2+ and Mg 2+ are the principal cations in the rainwaters and their mean values are 56.6 μmol/L (12.5–163.8 μmol/L) and 12.8 μmol/L (4.5–47.3 μmol/L ), respectively. The sum of Ca 2+ and Mg 2+ accounts for 78%–96% of the total cations in the studied rainwaters. Na + was the least abundant of the major cations with a mean content of 4 μmol/L (0.9–7.8 μmol/L). SO 4 2− is the predominant anion, with a mean content of 94 μmol/L (33.5–279.4 μmol/L), coming next is NO 3 − with a mean content of 48 μmol/L (2.1–251.8 μmol/L). SO 4 2− and NO 3 − together account for 77%–99% of the total anions. Ca 2+ and Mg 2+ in the rainwater are most likely from dissolution of carbonate minerals in dust or aerosol, unlike K + that shows more contribution of anthropogenic sources to the rainwater. Na + does not vary in concentration with Cl −. Significant enrichment of Cl − relative to Na + as compared with sea water indicates negligible contribution of marine source, which is supported by the evidence that the total rainwater samples show lower 87Sr / 86Sr ratios (ranging from 0.707934 to 0.709080) than sea water. The rainwater samples are characterized by high contents of NO 3 −, SO 4 2−, and Cl − relative to Na +, as compared to the rainwater from other areas in the world, suggesting that the anions (NO 3 −, SO 4 2−, and Cl −) have mainly of anthropogenic sources. Sr isotope shows potential to trace sources of contaminants when combined with other chemical factors: covariation of 87Sr / 86Sr ratio with Cl − / Na + in the rainwater suggest presence of at least two anthropogenic sources for the rainwater samples studied. The coal-combustion industries are probably the major atmospheric contaminant sources in Guiyang city.