A nanocomposite, silver nanoparticles embedded into polyethylene oxide (PEO) is synthesized by magnetron sputtering. The embedded silver in PEO matrix is confirmed by transmission electron microscopy (TEM) image, X-ray diffraction (XRD) pattern, and atomic force microscopy (AFM) analysis. By TEM image the sizes of silver nanoparticles are found to be tunable, and the silver crystallization is preferentially grown in facet of (111) by varying the plasma parameters, especially the working pressure. The crystal statue is evidenced by UV–visible spectra where the peak of plasmon absorption is located at ca. 400 nm. This characterization is very important for silver nanocomposite application as an antibacterial reagent based on previous antimicrobial results. By Fourier transform infrared spectroscopy (FTIR) the functional group of C–O–C in PEO films is depicted to be enough retained from the monomer in MS plasma.