Fast ignition (FI) of a conically guided DT assembly by a laser-accelerated deuteron beam is proposed. The uniformly pre-compressed fuel of 300 g cm−3 is heated by the deuteron beam of a Maxwellian energy distribution with a temperature of 3 MeV. This scheme makes full use of the deposited energy of the alpha particles produced by the athermal nuclear reactions and can save about 4.5% ion-beam energy compared with the FI by fast proton or carbon ion beams. The ignition energy delivered by the external beam can be reduced appreciably.