The alpha-particle emission spectrum in beam-injected deuterium-tritium (DT) plasma is examined by solving the Boltzmann-Fokker-Planck (BFP) equations for deuteron, triton and alpha-particle simultaneously. It is shown that owing to the existence of energetic component in fuel-ion energy distribution functions due to neutral-beam injection (NBI) and/or nuclear elastic scattering (NES), the fraction of the energetic (> 3.52MeV) alpha-particle generation rate increases significantly compared with the case for Gaussian distribution. Aiming at an application to plasma diagnostics, correlation between the modification of the emission spectrum and the gamma()-ray generation rate from 9Be(,n)12C reaction is studied.