Abstract: The wall rock of Zhaozhuang Coal Mine's secondary vertical shaft leaked seriously due to miniature cracks. After cement pre-grouting on the working face and cement grouting of backfilling, there was little improvement. However, through the new technology of chemical grouting of backfilling, the water yield falls to 2.5 m³/h, and the leakage drops by 97% and there has not been reverse osmosis since the completion of the project for 11 months. Therefore, it is clearly illustrated that chemical grouting is an effective way to prevent the leakage through miniature cracks.