Abstract: In order to study the stability of the floor aquiclude,based on the 'Down Three Zone' Theory,support pressure distribution law of the working face and the Thi n Plate Theory,combining with No.9103 working face mining and geological conditions,the floor aquiclude was simplified to four edges clamped rectangular plates under th e function of linear load. Floor aquiclude mechanics model was established to analyze the maximum flexure position,the direction of maximum principal stress and water inr ush criterion. The analysis showed that the maximum flexure position located at the intersection of the center of the tilt direction of the working face and the distance of wor king face coal wall first weight step distance's 51 12 times; the direction of maximum principal stress and horizontal principal stress direction was consistent in aquiclude; t he value of limit water pressure that aquiclude could bear and thickness of aquiclude showed a parabola relationship. The application of Thin Plate Theory in stability of flo or aquiclude was reasonable and feasible,providing a theoretical basis for mining above aquifer.