Differences in secondary structure among Bombyx mori (B. mori) silk and two wild silks of Antheraea yamamai (A. yamamai) and Antheraea pernyi (A. pernyi) were investigated by CP/MAS 13C NMR Spectroscopy. The β-sheet structure was primary in three silk, and B. mori silk had the highest β-sheet structure. Although amino acid compositions are very similar for two wild silk, their secondary structures had significant difference. A. yamamai silk contained more α-helix structure, whereas more β-turn and random coil structures formed in A. pernyi silk. B. mori silk was mainly composed of anti-parallel β-sheet structure, however, the parallel β-sheet structure was advantage in the two wild silks, and A. yamamai silk contained more anti-parallel β-sheet conformation than A. pernyi silk.