Carbon nanotips were prepared by plasma-enhanced hot filament chemical vapor deposition under different bias current using CH4, NH3 and H2 as the reaction gases, and investigated by scanning electron microscopy and micro-Raman spectrometer. The results indicate that the carbon nanotips have graphite structure. With increasing of the bias current, the tip angles of the carbon nanotips are reduced and their growth rate are increased. Combined with theory related to plasma and sputtering, the formation of the carbon nanotips and the change of their growth rate with the bias current are discussed.