Nanocrystalline　diamond　field　emitters　were　deposited　by　microwave　plasma-enhanced　chemical　vapor　deposition　using　porous　Si　as　host　matrixes.　Scanning　electron　microscopy　observations　showed　that　the　nuclei　of　diamond　occurred　at　the　edges　of　the　etched　pores,　and　the　nanoscale　diamond　grains　were　partly　embedded　into　the　pores　of　the　porous　Si.　The　structure　was　beneficial　to　the　electron　field　emission.　The　electron　emission　became　more　stable　and　the　emission　current　was　significantly　enhanced　comparing　with　those　of　the　diamond　films　deposited　on　Si　substrates　scratched　by　diamond　powder.