In　this　work,　a　novel　electromagnetic　wave　absorption　geopolymer　was　created　with　efficient　utilization　of　two　solid　wastes　iron　tailings　and　blast　furnace　slag,　meanwhile　the　mechanism　and　impacts　of　iron　tailings　content,　water-solid　ratio　and　specimen　thickness　on　their　electromagnetic　wave　absorption　and　mechanical　property　were　systematically　investigated.　It　was　found　the　pores,　micro-cracks　and　unreacted　particles　in　the　specimens　are　benefitial　for　electromagnetic　wave　absorption　but　against　to　compressive　strength,　even　though　the　compressive　strength　reaches　69.7　MPa　with　the　iron　tailings　content　50%　and　water-solid　ratio　0.4.　The　addition　of　iron　tailings　significantly　enhances　the　electromagnetic　wave　absorption　properties　of　the　geopolymers,　and　increasing　iron　tailings　content　improves　the　number　of　pores,　micro-cracks　and　the　permeability　of　geopolymers.　The　electromagnetic　wave　absorption　properties　of　the　geopolymer　initially　increase　and　then　decrease　with　the　increase　of　specimen　thickness　and　water-solid　ratio.　With　an　iron　tailings　content　70%,　water-solid　ratio　0.4　and　thickness　30　mm,　the　effective　absorption　bandwidth　(＜　-5　dB)　was　optimized　to　10.44　GHz　with　a　minimum　reflection　loss　of　-13.34　dB.　A　new　mechanism　for　electromagnetic　absorption　in　iron　tailings　has　been　proposed,　in　which　the　electromagnetic　wave　absorption　of　geopolymers　is　mainly　dominated　by　magnetic　loss　and　spatial　propagation　loss.　This　study　provides　higher　competitiveness　and　comprehensive　utilisation　of　iron　tailings　in　the　field　of　electromagnetic　wave　absorbing　building　materials,　and　has　great　potential　for　applications　in　military　and　other　fields　affected　by　high　electromagnetic　wave　frequencies.