This　study　aimed　to　investigate　the　evolution　of　compressive　strength　and　microstructure　of　hydrated　magnesium　silicate　(MgO-SiO2-H2O)　cement　with　Mg(OH)2　(MH)　as　a　modifier　under　standard　and　carbonation　curing　conditions.　Isothermal　calorimetry,　fourier　transform　infrared　spectroscopy　(FTIR),　X-ray　diffraction　(XRD),　and　thermogravimetry　analysis　(TGA)　were　used　to　analyze　the　hydration　rate　as　well　as　the　degree　of　hydration　of　the　MgO-SiO2-H2O　cements,　and　to　determine　the　types　of　the　physical　phases　and　the　mass　fractions　of　the　hydration　products.　The　porosity　structure　and　micro-morphology　of　MgO-SiO2-H2O　cement　were　characterized　by　mercury　intrusion　porosimetry　(MIP)　and　scanning　electron　microscopy　(SEM).　The　results　indicated　that　MH　could　slightly　enhance　the　fluidity　of　MgO-SiO2-H2O　cement.　As　the　dosage　of　MH　increased,　the　compressive　strength　of　MgO-SiO2-H2O　cement　showed　an　initial　increase　followed　by　a　decrease,　reaching　optimal　mechanical　properties　at　a　1　%　dosage.　The　addition　of　1　%　MH　accelerated　the　hydration　rate　of　MgO-SiO2-H2O　cement　and　the　formation　of　M-S-H　gel.　Carbonation　curing　could　convert　a　portion　of　MH　into　hydrated　magnesium　carbonates　(HMCs),　improving　the　utilization　of　MgO,　reducing　the　quantity　of　detrimental　pores,　and　decreasing　the　porosity.　Furthermore,　considering　the　synergistic　effects　of　MH　and　carbonation　curing,　the　performance　of　MgO-SiO2-H2O　cement　could　be　further　enhanced.