One　of　the　main　hurdles　for　the　wide　use　of　current　Ag-filled　conductive　composites　is　the　high　cost　of　Ag　fillers,　while　the　challenge　for　low　cost　copper-filled　composites　is　their　poor　reliability.　In　this　study,　the　Ag-coated　Cu　flakes　was　chosen　as　conductive　fillers　and　a　surface　modification　with　coupling　agent,　to　achieve　good　bonding　between　the　flakes　and　the　Polydimethylsiloxane　(PDMS)　matrix,　was　applied　to　improve　the　mechanical　and　conductive　properties　of　the　PDMS　based　composites.　The　resulting　composites　obtained　through　modification　showed　an　increase　in　hardness　by　13.1%　and　tensile　strength　by　28.4%　relative　to　the　composites　without　coupling　agent.　In　addition,　the　reliability　of　conducting　composites　was　discussed　and　the　results　showed　that　the　coupling　agent　played　a　great　role　in　preventing　the　corrosion　of　the　exposed　Cu　during　aging.　The　volume　resistivity　of　the　composites,　filled　with　untreated　Ag-coated　Cu　flakes,　increased　from　0.0039　Omega.cm　to　0.0059　Omega.cm　under　aging　at　85　degrees　C　and　85%　room　humidity　(RH)　in　a　temperature/humidity　chamber　for　48　h,　in　contrary,　the　volume　resistivity　shift　of　the　composites　with　treated　flakes　was　almost　negligible,　just　changed　from　0.0043　Omega.cm　to　0.0045　Omega.cm.　More　importantly,　the　prepared　conductive　silicone　rubber　filled　with　Ag-coated　Cu　flakes　with　the　resistivity　(0.004　Omega.cm)　comparable　to　the　relative　commercial　products　can　be　used　for　electro-magnetic　interference　(EMI).