Abstract: This paper describes the application of a new grouting system for water-blocking in Zhaogu No.2 Coal Mine.The mine adopted the geological transformation grouting system to grout the Taiyuan and Ordovician limestone aquifer，to block the permeable fracture，and also to transform the aquifer into aquitard or impermeable layer.The cement-clay mixed slurry with the density of 1.12~1.4 t/m3 was used in the system，and the slurry was pumped into underground at velocity of 34～250 L/min，with the pipeline's diameter of 41~50 mm.About 3 000 t cement has been grouted since the system was built in 2009，the system is stable in operation，and the effect of grouting is good.The system could totally meet the demand of underground water-blocking with economic benefits of 11 592 000 yuan achieved.

Key words: Coal mine grouting technology, Fracture blocking, Geological transformation, Water-blocking