Rainwater samples collected from Guiyang city in southwestern China between May 2009 and December 2010 were analyzed to measure their calcium and strontium isotope compositions. The results show that Ca²⁺ is the most abundant cation in these rainwater samples, while SO₄²⁻ is the most abundant anion. Most rainwater samples are alkaline, with a volume-weighted mean (VWM) pH value of ~6.2 (a 1.2-unit increase since 2008). This can be explained by the neutralization of rainwater acidity by the dissolution of atmospheric aerosols in the form of calcium-rich soil and other anthropogenic dust, which are increasing because of rapid urbanization. Both stable (δ^44/40Ca and δ^88/86Sr) and radiogenic (⁸⁷Sr/⁸⁶Sr) isotope compositions of rainwater show variations correlating with each other and with the inverse of Sr or Ca concentrations. They also correlated with the concentration ratio of (NH₄⁺+K⁺)/(Ca²⁺+Mg²⁺) ―an index reflecting the anthropogenic input relative to soil dust. Based on our results, three major reservoirs can be inferred to have contributed to rainwater chemistry in Guiyang city: (1) a carbonate aerosol source characterized by low ⁸⁷Sr/⁸⁶Sr (≤~0.708), δ^88/86Sr (≤~0.32‰) and δ^44/40Ca (~0.5‰), very low (NH₄⁺+ K⁺)/(Ca²⁺+Mg²⁺), and low 1/Ca²⁺ and 1/Sr²⁺; (2) a silicate aerosol source characterized by relatively high ⁸⁷Sr/⁸⁶Sr (≥0.717), δ^88/86Sr (≥~0.34‰) and δ^44/40Ca (~0.8‰), very low (NH₄⁺+K⁺)/(Ca²⁺+Mg²⁺), low 1/Ca²⁺ and 1/Sr²⁺; and (3) an anthropogenic component containing low ⁸⁷Sr/⁸⁶Sr (~0.708), δ^88/86Sr (~0.30‰) and high δ^44/40Ca (~0.8‰), and high (NH₄⁺+K⁺)/(Ca²⁺+Mg²⁺). The chemistry of solutes in Guiyang rainwater can be explained by (1) dissolution of carbonate and silicate aerosols, as well as the anthropogenic inputs including seasonal farming activities; (2) tightened environmental protection regulations; (3) higher precipitation volumes in 2010; and possibly (4) the increased combustion of coal for heating and electricity in winter. This study demonstrated that a combination of elemental compositions, stable Ca and Sr, and radiogenic Sr isotope compositions in rainwater can be used to trace the sources of atmospheric aerosols.