Fast ignition is a method in inertial confinement fusion (ICF) in which an ignition spark in pre-compression fuel is formed by an ultra-intense laser beam.In applying this method,a hot spot is built by relative electrons which are produced by the ultra-intense laser beam.For a better understanding,a fuel energy gain curve based on density is drawn and it can be observed that the ignition by an electron beam has the maximum energy gain.The maximum energy gain has been observed in equimolar DT fuel with a density of 500g/cm3 and in fuel with tritium (10％) with a density of 1000g/cm3.