Spider dragline silk is of great interest to people for its outstanding mechanical properties including high toughness. Biomimetic spinning of spider silk has attracted people's attention for decades. This paper reports a simple and cheap method to greatly toughen artificial silk by compositing with nanoanatase. The toughness of the artificial silk (breaking energy 93.1 ± 27.1 MJ m⁻³) exceeded that of silkworm silks. The hydrophilic nanomineral TiO₂ with large specific surface area interacted severely with the fibroin matrix through coordination complexes (Ti–protein) and hydrogen bonds (O–H). Due to the interfacial interactions, regenerated silk fibroin (RSF)–TiO₂ fibers showed higher α-helix/random coil content, lower β-sheet content, smaller crystallites and lower crystallinity than pure RSF fibers. A nanoconfined crystallite toughening mechanism was proposed to discuss the structure–property relationship of the hybrid fibers.