Gold nanoparticles were precipitated on the surface of silica gel without mechanical mixing. Polyethylenimine (PEI) which was coated on the surface of silica gel reduced raw materials of hydrogen tetrachloroaurate (III) tetrahydrate (HAuCl₄4H₂O). Formation of gold nanoparticles on silica gel was confirmed by using Field Emission Scanning Electron Microscope (FE-SEM) and Energy Dispersive X-ray Fluorescence Spectrometer (EDX). In this study, particles size distribution and coverage ratio of gold on silica gel were investigated.