In　this　study,　copper　slag　reprocessing　tailings　(CSRT)　were　synthesized　into　geopolymers　with　40%,　50%　and　60%　metakaolin.　The　evolution　of　compressive　strength　and　microstructures　of　CSRT-based　geopolymers　in　a　marine　environment　was　investigated.　Except　for　compressive　strength　measurement,　the　characterizations　of　X-ray　diffraction　(XRD),　Fourier-transform　infrared　spectroscopy　(FTIR),　nuclear　magnetic　resonance　(NMR)　and　scanning　electron　microscopy　(SEM)　were　included.　It　was　found　that　marine　conditions　changed　the　Si/Al　ratio　in　the　sodium-aluminosilicate-hydrate　(N-A-S-H)　gel　backbone,　promoted　the　geopolymerization　process,　led　to　more　Q4　(3Al),　Q4　(2Al)　and　Q4　(1Al)　gel　formation　and　a　higher　compressive　strength　of　the　geopolymers.　This　provided　a　basis　for　the　preparation　of　CSRT-based　geopolymers　into　marine　concrete.　©　MDPI　AG.　All　rights　reserved.