Abstract: The kast and fault development in limestone K₂ of Carboniferous Taiyuan formation has induced complex hydrogeological conditions in Liyazhuang mining area.. In order to solve the problem of water inrush evaluation in the floor of the second seam in the limestone of upper Taiyuan formation, we used the AHP vulnerability index method of GIS. Compared with the traditional water inrush coefficient method, the vulnerability index method reflects more comprehensive relative fragile relationship of different areas and the result is more practical and reliable.