Enzyme-induced　carbonate　precipitation　(EICP)　is　an　emanating,　eco-friendly　and　potentially　sound　technique　that　has　presented　promise　in　various　geotechnical　applications.　However,　the　durability　and　microscopic　characteristics　of　EICP-treated　specimens　against　the　impact　of　drying-wetting　(D-W)　cycles　is　under-explored　yet.　This　study　investigates　the　evolution　of　mechanical　behavior　and　pore　characteristics　of　EICP-treated　sea　sand　subjected　to　D-W　cycles.　The　uniaxial　compressive　strength　(UCS)　tests,　synchrotron　radiation　micro-computed　tomography　(micro-CT),　and　three-dimensional　(3D)　reconstruction　of　CT　images　were　performed　to　study　the　multiscale　evolution　characteristics　of　EICP-reinforced　sea　sand　under　the　effect　of　D-W　cycles.　The　potential　correlations　between　microstructure　characteristics　and　macro-mechanical　property　deterioration　were　investigated　using　gray　relational　analysis　(GRA).　Results　showed　that　the　UCS　of　EICP-treated　specimens　decreases　by　63.7%　after　15　D-W　cycles.　The　proportion　of　mesopores　gradually　decreases　whereas　the　proportion　of　macropores　increases　due　to　the　exfoliated　calcium　carbonate　with　increasing　number　of　D-W　cycles.　The　microstructure　in　EICP-reinforced　sea　sand　was　gradually　disintegrated,　resulting　in　increasing　pore　size　and　development　of　pore　shape　from　ellipsoidal　to　columnar　and　branched.　The　gray　relational　degree　suggested　that　the　weight　loss　rate　and　UCS　deterioration　were　attributed　to　the　development　of　branched　pores　with　a　size　of　100–1000　μm　under　the　action　of　D-W　cycles.　Overall,　the　results　in　this　study　provide　a　useful　guidancee　for　the　long-term　stability　and　evolution　characteristics　of　EICP-reinforced　sea　sand　under　D-W　weathering　conditions.　©　2023　Institute　of　Rock　and　Soil　Mechanics,　Chinese　Academy　of　Sciences