Pure Poly methyl methacrylate (PMMA) thin films and PMMA mixed with 1 %, 3%, 5% &7% by weight of ZnS nanoparticles (NP) were prepared by plasma jet technique. Formulation of the polymer with nanoparticles allows for modification of polymer physical properties. The PMMA /ZnS nanocomposite prepared by polymerization in plasma jet and characterized by Ultra Violet Visible UV-Vis, Fourier Transform Infra-Red Spectrophotometer (FTIR), Atomic Force Microscopy (AFM) and SEM to study the effect of ZnS nanoparticles on the optical properties, morphology and structure of the thin films. The FTIR spectra for the films show an interaction between PMMA and NPs. There is a decrease in the optical band gap of films prepared with an increase of the concentration of NPs. AFM and SEM images show that there are a few clusters of ZnS and there is a homogeneous distribution of the nanoparticles in the PMMA matrix.