A mathematical model and a program are developed to calculate neutron yields, energy spectrum and angular distribution of D (d, n)³He reaction in a thick deuterium-titanium (TiD_x) target as incident deuteron energy lower than 1.0 MeV. D(d, n)³He reaction cross section from nuclear data tables and stopping power derived with SRIM-2003 code are adopted in the calculatoin of neutron production of an accelerator-based D(d, n)³He reaction neutron source. Integrated neutron yields, neutron energy spectrums and angular distribution are obtained.