Abstract: The shielding properties and mechanical properties of high density polyethylene/lead-boron composite were studied. The effects of density and B4C content on shielding performance are compared by shielding simulation, and the effects of B4C content on shielding performance, bending strength and impact strength are compared by experiments. The simulation results showed that the thermal neutron shielding performance and gamma shielding performance increases ,yet the fast neutron shielding performance decreases with the improved of the density of polyethylene / lead?boron composite. The neutron shielding performance decreases with the increase of B4C content while keeping the density of composite unchanged. The experimental data show that with the increase of B4C content, the fast neutron shielding performance and thermal neutron shielding performance of polyethylene/lead-boron composite decrease, while the gamma shielding coefficient increases, but the overall change is not obvious; the impact strength and the bending strength of the material decreases obviously. The simulation results and experimental data show that the high density polyethylene/lead-boron composite containing about 2 % B4C has better shielding performance and mechanical properties meanwhile.