A　double　layer　radar　absorbing　structure　(RAS)　with　excellent　radar　absorption　property　in　X　and　Ku　band,　has　been　designed　based　on　the　calculated　permittivity　requirements　according　to　the　transmission　line　theory.　The　two　kinds　of　SiC　fibers　with　different　resistivity　reinforced　epoxy　(SiCf/epoxy)　are　chosen　and　constructed　to　serve　as　the　lossy　layer　and　matching　layer,　respectively.　The　fiber　volume　fraction　of　the　two　layers　are　specified　according　to　volume　fraction　dependent　dielectric　properties　of　the　designed　composites,　which　is　determined　by　the　different　characteristics　of　SiC　fibers.　The　thickness　dependent　absorption　property　of　the　double　layer　SiCf/epoxy　is　calculated　and　investigated.　Radar　wave　absorbing　performance　of　the　designed　SiCf/epoxy　is　measured　and　the　fabricated　composite　with　the　total　thickness　of　4.6　mm　shows　more　than　90%　absorption　in　the　whole　X　and　Ku　band　when　the　incident　angle　is　less　than　30　degrees.　Furthermore,　the　multi-scale　radar　wave　absorption　mechanism　for　the　fabricated　double　layer　RAS　is　discussed　based　on　the　multi-scale　structure　of　the　fabricated　composite.