The conformation of silk fibroin in silk fibroin/chitosan (SF/CS) blend membrane was analyzed by infrared spectrum, X-ray diffractometry, and Raman spectrum. The results demonstrated that the SF could show beta-sheet conformation when the SF content in blend membranes was 10% (w/w) and 60-80% (w/w), while the pure SF membrane showed random coil conformation. A mechanism of the conformation transition was suggested in that the SF chain could use the rigid CS chain as a mold plate to stretch itself to form a beta-sheet structure according to the strong hydrogen bond between CS and SF. Therefore, a new concept, named "Polymer-Induced Conformation Transition," was proposed.