Abstract: To minimize the size and weight of the vehicle-mounted accelerator-driven D-D neutron source, optimization of compact and lightweight radiation shielding material for the fast neutrons was carried out, which employed genetic algorithms and the MCNP code. Based on this method, a series of material samples were designed and the shielding performance was compared with that of traditional materials such as PB202, PE-30%B, M-L1 and M-L2 for the D-D neutron by MCNP. To compare the shielding performance conveniently, both of the needed volume and weight were compared while assuming the shielding as a coaxial tapered cylinder. The results show that the SDGa can satisfy the requirements of lightweight and compact simultaneously. At the same time, the activation gamma dose rates of SDG3 and SDG3* after 1 000 h irradiation were evaluated, and the results show that the activation can be neglected.