Abstract: Yuanbaoshan open-pit coal mine of Inner Mongolia is a rare extra large water rich open-pit coal mine at home and abroad. In order to resolve the problems of high production cost and high environmental risk caused by drainage for many years, it is plan to adopt water cutoff curtain technology to closure the seepage supply channel. By analyzing the hydrogeological and engineering geological conditions of the mine, the groundwater water control method of combining arc semi-closed curtain with group wells drainage hydraulic curtain was proposed. The curtain test study was carried out in the mine 452 m flat plate by using the vertical concealed overlay laying of geomembranes and the filling process of impermeable concrete. A water cutoff curtain with a plane length of 1 369 m, an average depth of 29 m, an effective thickness > 0.8 m and bottom embedded in bedrock surface of 3 m was built, During the test study, the technology of water cutoff curtain was determined in Yuanbaoshan open-pit mine. The main technical parameters such as the excavation length of single trench section (14 m), the retaining wall mud density (1.05-1.25 g/cm ³) and the overlapping width of the geomembrane (1 m) were obtained, and the technology of underwater magnetic suction connection of geomembranes was put forward, by adding magnetic strips, the underwater self-adhesion of the geomembrane overlaps on the principle of Yin-Yang magnetic suction was accomplished. After the experiment project, the quality and water interception effect of curtain wall were tested by drilling verification, flow field analysis and runoff changes. The results show that the concrete pouring and filling is continuous and the water level difference between inside and outside of the wall has reached more than 15 m; the recharge flow of blind-ditch disappears, and the water interception effect is remarkable. The experimental research proves that the water interception curtain technology is suitable for Yuanbaoshan open-pit coal mine, and provides key technical parameters for the follow-up project, improves the water interception curtain technology system of open-pit coal mine of China.