Abstract: Through the test for the chilled water flow of the composite water supply pipeline system with open-supply and close-return in Tangkou Coal Mine underground of Shandong Province, it analyzed the effective water supply and water utilization ratio underground. The results showed that the effective water supply was insufficient and the water fluctuating range was large, the average utilization ratio of the chilled water was not over 40% for the whole mine, and the effective water flow was not over 64 m³/h. At the same time, this way had some problems, such as the water requirement for cooling and non-cooling operations were difficult to meet simultaneously, and the supply and the demand for cooling water were not consistent. It pointed out that the utilization ratio for cooling water would further decrease, and the cooling water would be more difficult to meet with the mining area pioneering. So it was urgent to improve the supply way for cooling in order to increase the water utilization ratio.