Abstract: Optimized in lightweight, compactness and high temperature sustaining the shielding materials for neutron and gamma radiation were designed based on genetic algorithms. Three kinds of materials studied by this method were designed and simulated with MCNP code, and results were compared with those from iron etc. The total shielding effects of the materials with certain thickness for fission neutron and γ-ray are all much better than iron, and the equivalent masses are lower than iron at same shielding effect.