Abstract: The grouting subsidence reduction technology of overburden bed separation is one of the key technologies for the protection of surface buildings in mining areas, By injecting slurry into the overburden strata, it plays a role of filling and supporting, thus weakening the subsidence of key strata and surface subsidence. Meanwhile, the stability of the slurry barrier layer is a key link to ensure the occurrence and control flow of the slurry, and its inaccurate determination will increase the risk of underground safety. In view of the above problems, a“mechanics-seepage” double criterion model for the stability of the slurry layer is proposed by means of theoretical analysis, laboratory test and field monitoring, and the potential flow path of the grouting slurry and the stability of the slurry layer are studied. Through theoretical analysis, the potential flow path and loss mechanism of slurry under different geological conditions are clarified. Based on the stress and deformation characteristics of the slurry layer and Darcy's law, the maximum bending subsidence value and the height of the free space below it are calculated. The permeability coefficient is introduced and the seepage velocity of the slurry bleeding water is calculated. The stability of the slurry layer is evaluated from the two dimensions of mechanics and seepage. The bleeding rate and viscosity index of the slurry under different concentration conditions were determined by laboratory tests, and the total amount of bleeding was estimated based on the bleeding rate. Taking the 11030 working face of a mine as an engineering example, the model is used to evaluate the stability of the slurry separation layer, and the risk of underground water inrush is effectively predicted. Through the analysis of the water inrush quality and the water inrush situation of the adjacent working face, it is confirmed that some of the water inrush comes from the slurry secretion, which further verifies the effectiveness and applicability of the proposed model. This study provides a theoretical basis and practical reference for the parameter optimization and safe construction of overburden separation grouting engineering.