<p>Water-inrush and sand-inrush disasters caused by mining in weakly cemented strata in mining areas such as the Ordos Basin and Eastern Inner Mongolia have become more common. Using Zhaoxian, Xinshanghai No.1, and Luxin coal mines as research subjects, this study reveals the sedimentary environmental control mechanisms of weakly cemented strata through macro-mechanical testing, microstructural analysis, and sedimentary environment research. Weakly cemented rocks are generally constituted of quartz and clay minerals, with argillaceous contact-type or pore-filling cementation being the most common cementation types, manifesting mostly as argillaceous cementation. These features contribute to their “low strength, high porosity, and water-sensitive” qualities. In sedimentary environments, high-energy fast deposition produces weakly cemented structures composed of coarse clastic particles, whereas low-energy still-water sedimentation promotes clay mineral enrichment. Both mechanisms cause insufficient cementation and reveal the development patterns of weakly cemented strata in tectonically active zones. Under water–rock contact, hydration swelling of clay minerals causes particle separation, structural instability, and eventually overall disintegration, resulting in a sequential degradation process defined as “surface wetting-bubble ejection-local spalling-overall disintegration.” This work demonstrates a progressive link between “sedimentary environment-microstructure-mechanical properties” giving a sedimentological and microstructural characteristics foundation for anticipating water risks and assessing engineering stability in weakly cemented strata.</p>