To overcome the bacteria-caused degradation of silk, an ultraviolet light (UV)-assisted in situ synthesisapproach is developed to immobilize silver nanoparticles (AgNPs) on degummed silk fibers for antibac-terial applications. Results show that AgNPs with excellent crystalline structures are efficiently attachedon the silk surface in an irradiation time-dependent manner. The immobilization of AgNPs could greatlydelay the thermal degradation of silk. The antibacterial activity of the AgNPs-coated silk is evaluatedby the growth curve of bacteria, zone of inhibition and dual staining assays, clearly demonstrating itsbacterial growth inhibition ability and bactericidal effects. This work offers potentials to produce specificAgNPs-coated antimicrobial silk for various applications in textile industry.