To tackle the severe plastic pollution, degradable materials with excellent mechanical properties are urgently needed. Silk protein materials with abundant sources, low cost, and good biocompatibility can be ideal candidates. However, due to the destruction of the original hierarchical structure of natural silk during processing, the mechanical properties of regenerated silk are usually significantly reduced. Here, we report a general strategy for constructing regenerated silk fibroin composites with high mechanical properties by introducing oriented nanoconfined β-crystals. Specifically, regenerated silk was introduced into the two-dimensional nanoconfined space of montmorillonite nanosheets, and an alcohol reagent was used to induce its secondary structure to transform from random coils/α-helices/β-turns to β-sheets, further forming β-crystals. These materials exhibit excellent mechanical properties with a tensile strength of 452.31 ± 21.23 MPa and modulus of 21.67 ± 0.24 GPa, superior to most plastics and polymer nanocomposites. In addition, these materials are biodegradable and can be fabricated in large areas.