Abstract: he secondary neutron emission doubledifferential cross section (DDX) of natural iron induced by 8.17 MeV neutron was measured. The neutron emission energy spectra were measured at 11 different angles from 30° to 150°. The results were normalized to np scattering measurement. The measured data were analyzed by MonteCarlo simulation for the corrections of neutron fluence attenuation, multiple scattering and finite geometry. The measured results were compared with the evaluated data and the other measurements. The experimental result will contribute to the nuclear data evaluation, the theoretical model calculation and the nuclear data applications.