For inertial confinement fusion experiments, a copolymer of acrylonitrile and styrene (AS) shell overcoated with a cross-linked polyvinyl alcohol (PVA) has been fabricated in order to obtain good gas-barrier properties and resistance to beta decay of tritium. The fabrication method is based on the emulsion method using the interfacial poly-condensation reaction between water and oil phases. Cross-linked PVA with a thickness of 5 mu m has been successfully overcoated on an AS shell. The surface roughness has been estimated using an atomic force microscope to be 0.5 nm (root mean square).