This paper provides a quantitative method to research karst water from different strata and a scientific basis for karst water resources evaluation and reasonable exploitation. The analysis of different water samples collected from Xishui Basin reveals that the underground water flowing through different rock formations varies in the value of Sr2+ , Sr/Ca, Sr/Mg. Generally, the bedrock fracture water flowing through the sandstone formation contains low Sr2+ with high Sr/Ca and Sr/Mg. Recharged by the water from limestone or coal formation, the fracture water of sandstone is high in content of both Sr2+ and Sr/ Ca, Sr/Mg value, while the water flowing through limestone has lower Sr/Ca value and higher Sr/Mg value than that (flowing) through dolomite formation. The Sr/Ca and Sr/Mg value in outlet water of underground river ranges between those of other types of water, so the proportion of different types of water can be calculated by the Sr/Ca and Sr/Mg value, and the contribution of allogenic water to underground river can be determined.