Silver nanoparticles (AgNPs) with diameter about 8 nm were immobilized on the surface of cotton fabrics by y-irradiation of fabrics in the AgNO3 chitosan solution. Effect of absorbed dose on immobilization of the AgNPs on fabrics was investigated. The optimal dose was selected to be 13.8 kGy at concentration of AgNO3 was 1.5 mM in 1 percent chitosan solution. The maximal content of AgNPs on fabrics was of 1696 mg/kg. The presence of AgNPs on fabrics was confirmed from scanning electron microscopy (SEM) images and X ray diffraction (XRD) patterns. The antibacterial activity of cotton-AgNPs fabrics after washings against S. aureus and E. coli was found to be 99.99 percent. In addition, the AgNPs fabrics were innoxious to the skin (k=0) after 1, 5, 10,20,30 and 40 washings by skin-irritation testing to animal (rabbit).