This study on adding various mixing ratio of chitosan / gelatin into silk fibroin and nano fiber membrane was prepared by electrospinning .The fineness and antibacterial properties of membranes were investigated . The results showed the fibers were more uniformed and fineness increasing with increase of concentration of gelatin. In addition, the antibacterial properties were obviously enhanded by adding chitosan. The concentration of chitosan was at 7%, the antimicrobial ratio arrived 99.5%. The nano fiber membranes made from mixture of silk fibroin/chitosan/gelatin were environmental and available for biomaterials. The structural properties of chitosan cause the water absorption to decrease with an addition of chitosan.