Abstract: The open pit coal mines in China are mainly distributed in the ecologically fragile areas in western China, and the groundwater is mainly controlled by drainage, which leads to the decrease of the groundwater level and vegetation coverage around the mining area.Therefor, the groundwater resources and ecological environment are both affected to varying degrees. In order to solve the water resources and ecological and environmental problems caused by coal mining, the approach of building underground seepage prevention curtain wall was proposed since the 1990s. Based on it, it has developed some key technologies such as impermeable membrane and impermeable material composite technology, low intensity water cutoff wall technology and ultra-high pressure angle domain jet grouting technology for open-pit coal mine ecological groundwater protection, which were applied in Zhanihe open-pit coal mine. Results show that the active water protection technology applied in the open-pit coal mine achieved a great success in high efficiency, cost saving and environmental protection effect. The drainage volume of the open pit coal mine decreases gradually at a reduction rate of 75.00%. The underground water level around the open pit coal mine is steadily raising and now the underground water level restores to the original water level before mining. The vegetation coverage increases year by year, from less vegetation to moderate vegetation. The active water protection technology based on ecological water level can be further applied in understand mines and non-coal mines, so as to preserving the ecological underground water level and realize the reduction of losses and green mining.