Abstract: To satisfy requirements for flexible neutron shielding composite of complex shape of nuclear equipment outer protection and radiation protection clothing, a new type B₄C/SEBS flexible neutron shielding composite was prepared. The effect of the mechanical properties, thermal properties and neutron shielding performance of SEBS composites with different B₄C contents was studied. The experimental results show that the tensile strength and elongation at break of composite materials decrease with the increase of B₄Ccontent. With the increase of B₄C content, the tearing strength of composites increases first and then decreases, while the Shore hardness of composites increases. The thermal conductivity of the composite materials increases with the rise of B₄C content. The neutron shielding performance was tested by using americium-beryllium neutron source, and with the same thickness of the material, the more content of B₄C, the better of neutron shielding performance. Considering the excellent neutron shielding performance, tear strength and flexible of the composite, it has a large potential application in the protective material of complex shape of nuclear equipment and neutron shielding clothing.