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Silk has poor antibacterial and UV protection properties which limit its application fields. Silver nanoparticles (AgNPs) have attracted great attention due to their excellent antibacterial activity. This work proposed a green and efficient way to prepare AgNPs from silver nitrate using the aqueous extract from tea stem waste, and a functional finishing of silk material with the resulting AgNPs by an immersion technique. AgNPs prepared at pH 9 and 40 ℃ exhibited ultra-fine particle size (<20 nm), good dispersibility and good storage stability. When silk was treated with AgNPs at pH 3 and 80 ℃ for 40 min, it displayed high silver content and color depth. The antibacterial and UV protection ability of AgNPs treated silk fabric of crepe de chine (52 g/m2) increased as the silver content of silk increased. At a silver content of 3.64 mg/g, the antibacterial rate of treated silk against Escherichia coli and Staphylococcus aureus was as high as 99%, and it was above 92% even after 20 cycles of washing under a neutral condition. At the same silver content, the UV protection factor of treated silk reached 21.3, being classified as “good protection”. The present study not only presents a novel approach for the functionalization of silk material using biosynthesized AgNPs, but also implements the reuse of tea stem waste.