In order to improve the water-solubility of chitosan, N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (quaternary chitosan) was synthesized by the heterogeneous reaction between glycidyl-trimethyl-ammonium chloride and chitosan. The quaternary chitosan was then applied to Antheraea pernyi (A. pernyi) silk filaments/fabrics in the presence of 1,2,3,4-butane tetracarboxylic acid (BTCA). The structure and properties of A. pernyi silk before and after treatment were studied. It was found that the quaternary chitosan treatment contributed to enhance the mechanical properties including breaking strength, breaking elongation, initial modulus, rupture work and wrinkle-resistant performance of the A. perny silk filaments. When dyed with acid dyes, the dyeing uptake and shade depth of the quaternary chitosan treated A. perny silk fabrics were greatly improved.