Abstract: 6LiD neutron source, which converts thermal neutrons from the reactor into fusion neutrons, is useful in the field of the material research in fusion neutron irradiation environments. The process of fusion neutron production in6LiD is simulated from Monte-Carlo methods, which indicates the feasibility of the type of neutron source in theory. In the paper, the calculation result shows that every one thermal neutron acts on the outside surface of the converter, 0.131 4 fusion neutrons with a spectrum ranging from 13.5 to 15.5 MeV are produced inside the converter.