Abstract: The chemical composition of spring water is increasing year by year, and there are many factors affecting water quality. There are three "limestone skylight" distributed in and near the exposed area of Jinan spring group, with an area of about 0.6 km². They are the hydraulic connec-tion point between pore water and karst water, which is easy to cause spring water pollution. Based on the test data of groundwater samples around the "limestone skylight" and the test data of skylight karst water and regional karst water samples, the hydrochemical components are studied by using the theory of hydrodynamic field and hydrochemical field.The results show that the pore water of "limestone skylight" is easy to be polluted. The pore water level in dry season is higher than that of karst water and the polluted pore water supplies karst water.Therefore, the "limestone skylight" is one of the factors affecting the Hydrochemical Composition of spring water.