We investigated the effect of the thin film by plasma polymerization on color depth of polyester(PET) fabric. We obtained the plasma polymerized tetramethylsilane(PP-TMS) on the fabric by the 13.56MHz RF glow-discharge method using tetramethylsilane(TMS) monomer, This monomer shows lower refractive index(n,: 1.3585)than that of polyester fabric(nv= 1.725). The chemical structure and the optical characteristic of PP-TMS have been studied with a control of discharge power W and feed-in rate of monomer Fm. From IR spectra, we observed that Si-H and Si-CHa-Si bonds were newly generated in PP-TMS, and the relative absorbance ratio of Si-CH2-Si (1045cm-1) onto CHI(1255cm-1) was gradually increased with the value of composite energy W/Fm. PP-TMS showed high hydrophobicity, and surface energy(32~36dyne/cm2) was increased with W/Fm value. We could know that the reflectance(%) and L value of the PET fabric plasma polymerized with TMS were lower than those of untreated PET fabric. From those results, PP-TMS coatings were effective on the color depth of PET fabric and these phenomena could be explained by optical theories relating to surface reflection.