The effect of D-sodium erythorbate on the setting time, conductivity, compressive strength, and water resistance of magnesium oxysulfate cement was investigated. The phase composition and microstructure of hydration products of magnesium oxysulfate cement were analyzed using X-ray diffraction, synchronous thermal analysis, and scanning electron microscopy. The results show that the addition of chemical additive D-sodium erythorbate significantly prolongs the setting time of magnesium oxysulfate cement. Additionally, the formation of a substantial amount of 5Mg(OH)₂· MgSO₄·7H₂O(5·1·7) crystalline phase greatly improves the compressive strength and water resistance of magnesium oxysulfate cement.