The　electrical　and　optical　properties　of　the　indium　tin　oxide　(ITO)/epoxy　composite　exhibit　dramatic　variations　as　functions　of　the　ITO　composition　and　ITO　particle　size.　Sharp　increases　in　the　conductivity　in　the　vicinity　of　a　critical　volume　fraction　have　been　found　within　the　framework　of　percolation　theory.　A　conductive　and　insulating　transition　model　is　extracted　by　the　ITO　particle　network　in　the　SEM　image,　and　verified　by　the　resistivity　dependence　on　the　temperature.　The　dependence　of　the　optical　transmittance　on　the　particle　size　was　studied.　Further　decreasing　the　ITO　particle　size　could　further　improve　the　percolation　threshold　and　light　transparency　of　the　composite　film.