Groundwater is one of the important factors controling the accumulation and exploitation of coal measures gas. In this work, a water source identification method based on hydrochemistry, stable isotope, I-129 and C-14 dating is first established; then, the source, age, and evolution of coal measures water in the Central-South Qinshui Basin are clarified. The results reveal that the hydrogeological environment of coal measures water in Carboniferous-Permian is between semiclosed and open, with free water exchanging. The coal measures water in the Guxian and Shizhuangnan blocks are Ca-HCO3 and NaHCO3 types, respectively, while the closed coefficients are 1.77 and 322.75, respectively. Therefore, the water is attributed to river water or shallow groundwater in the Guxian block and deep groundwater in the Shizhuangnan block. The age of coal measures water is 1.51-20.61 Ma, which indicates that the water in coal measures at the present stage is a mixture of a little paleo sedimentary water and massive modern meteoric water and that the modern meteoric water recharge lasted until 1950. The above achievements deepen the understanding of the coal measures reservoir type and also guide the optimal selection and co-exploration and-exploitation of coal measures gas.