Abstract: In order to identify water-inrush source of poor sealed borehole under the compound aquifer, based on the analysis of hydrogeology and hydrochemistry conditions in coal mining, Quaternary and Yan'an formation which were not water-inrush source were excluded. Zhiluo formation and its lower segment aquifer may be water-inrush resource. Because of the similarity of Zhiluo formation and its lower segment aquifer's water yield property and hydrochemistry conditions, fuzzy clustering analysis was adopted. K⁺ + Na⁺、Ca²⁺、Mg²⁺、Cl^-、SO₄^2- 、HCO₃^- in water-inrush point, Zhiluo formation and its lower segment aquifer were selected as evaluation index. Matlab was used to calculate and the water samples were divided into two types; the water sample of water-inrush point was the same as Zhiluo formation lower segment aquifer. After determination of water-inrush source, the poor sealed borehole was sealed. For similar hydrogeology and hydrochemistry conditions of aquifer, fuzzy clustering analysis is effective method to identify the water-inrush resource.