Evolvement of bioinspired approaches for the construction of well-ordered nanostructures is a crucial intersection of branches of materials science and biotechnology. In this paper, floriated clusters of silver nanocrystallites, which consist of polycrystalline grains about 5 nm in diameter, have been successfully prepared on silk fibroin fibers (SFFs) through an in situ biotemplate redox approach at room temperature. The reductive amino acid tyrosine of SFFs mainly provided both reduction and location functions under alkaline conditions and could reduce Ag(I) ions to Ag(0). Finally, stable silver nanoclusters were generated on SFF substrates. The morphologies of silver nanoclusters were mostly attributed to the concentration of silver nitrate solution as well as special configurations and structures of silk fibroin macromolecules. A possible mechanism was explored intensively for tyrosine-residue-based silver nanocrystal formation.