Green synthesis of silver nanoparticles (AgNPs) using the silk sericin (SS) solution by in situ reduction at room temperature is reported. The effect of pH on the reduction reaction is studied by UV-Vis spectroscopy. The structure of the sericin-based silver nanoparticles is characterized by TEM. According to the TEM images, the average size of the silver nanoparticles is about 16 nm. The silver nanoparticles are highly dispersed and stable in silk sericin solution for monthes.