ABSTRACT In response to the dynamic hazards caused by the fracture of thick‐hard strata in deep mining, this study investigates their progressive breaking law by integrating theoretical analysis based on thick plate theory with physical simulation experiments. A self‐developed simulation device and a corresponding mechanical model were employed. The research identified and validated four characteristic fracture modes of the strata: “C‐Y,” double “Y,” “π,” and “Y” modes, and clarified their mechanical origins and occurrence conditions related to face length and advancing distance. Furthermore, the destabilization process was proposed to follow a three‐stage sequence: overhanging, fracture, and rotation or sliding (the O‐F‐R or O‐F‐S model). This model particularly elucidates the sliding instability prevalent in western Chinese mining areas. The work revealed that increasing strata thickness significantly amplifies shear effects and the risk of sliding instability. These findings establish a theoretical foundation for the mechanism analysis and control of strong ground pressure induced by thick hard strata.