The　investigation　is　concerned　with　the　utilization　of　the　strain　energy　based　finite　element　method　and　the　damping　properties　of　the　unidirectional　lamina　for　predicting　the　modal　loss　factor　of　fiber　reinforced　composite　structure.　The　results　for　the　vibration　and　damping　analysis　of　laminated　plates　obtained　by　the　present　method　were　compared　with　the　results　obtained　by　other　authors　to　verify　the　reasonability　of　the　present　method.　Contributions　of　3-D　stress　components　to　damping　can　also　be　studied　by　this　method.　The　modal　loss　factor　of　an　orthogrid-stiffened　composite　panel　was　studied　by　using　the　present　method　and　particular　attention　was　paid　to　the　effect　of　ribs　on　damping.