Carbon　nanotubes　were　catalytically　grown　by　negative　bias-enhanced　hot　filament　chemical　vapor　deposition　at　low　substrate　temperature　(550°C)　and　their　growth　was　investigated　by　scanning　electron　microscopy.　It　is　found　whether　the　carbon　nanotubes　could　be　orientationally　grown　at　low　temperature　depended　on　the　plasma　power　and　carbon　nanotubes　could　not　be　grown　if　the　pressure　was　too　low.　The　analysis　results　by　the　related　theory　indicate　that　the　interaction　of　the　strong　electrical　field　formed　by　plasma　with　the　catalyst　particles　resulted　in　the　orientation　growth　of　carbon　nanotubes　when　the　plasma　power　was　large　and　the　diffusion　of　the　particles　containing　carbon　at　low　pressure　was　too　fast　to　grow　the　carbon　nanotubes.