Actinomycetes genus streptomyces is a gram positive bacteria that has a high content of guanine and cytosine, and also enzyme nitrate reductase in extracellular fluid. The formation of silver nanoparticles with actinomycetes is scientifically suggested through the involvement of the enzyme nitrate reductase modifying silver ions into silver nanoparticles. The aim of study is evaluate the potency of extracellular fluid of streptomyces strain SM 4 as a bioreductor in the synthesis of silver nanoparticles along with the antibacterial activity. The experiments had been conducted by mixing the extracellular fluid from 11 days fermentation of strain sm 4 with 1 mm silver nitrate solution. As the results, 11 days fermentation of extracellular fluid from strain SM 4. The silver nanoparticles products were observed with uv-vis spectrophotometry at a wavelength of 415 nm, absorbance of 1.039 with an estimated particle size of 35 to 50 nm. Furthermore, in term of antibacterial activity assay, silver nanoparticles inhibit the formation of on Escherichia coli and Staphylococcus aureus were 9.822 mm and 8.956 mm, respectively. Streptomyces strain sm 4 can be used as a bioreductor in the synthesis of silver nanoparticles detected at a wavelength of 415 nm with an estimated size of 35-50 nm. The antibacterial activity of the silver nanoparticles formed can inhibit the growth of E.coli and S.aureus bacteria.