the mono-energetic neutron spectra for En= 5 MeV and 2 MeV from accelerator D(d
n) reaction were measured.The spectrum measurement of neutrons emitted from thick beryllium target irradiated by 3 MeV or 1.5 MeV d beams from the 4.5 MV accelerator at Peking University was performed.The results agree with that of the time-of-flight method.