Abstract: In order to prevent water inrush from the lower coal seam of the thin limestone aquifer of Taiyuan Formation during mining，the multi-branch horizontal directional drilling technology was applied before mining in the southwestern part of the northern Yellow River. The aquifer with an average thickness of 10 m was reinforced by grouting，and the aquifer was transformed into a weak aquifer or aquiclude. In order to explore the influence range and transformation effect of grouting slurry，the distribution of borehole water level was analyzed by statistics. The grouting process of multi-branch horizontal wells can form obvious water-blocking and water-resisting areas，and the effect of reconstruction of thin limestone aquifer in Taiyuan Formation is obvious. The denser the drilling arrangement is，the better the reconstruction effect is. This practice provides experience and technical support for the reinforcement and treatment of thin lime⁃ stone aquifer.

Key words: horizontal directionally drilled, thin limestone, grouting, water damage prevention