The effects of dolomite powder on the sulfate resistance of cement-based materials with water-binder ratio (w/b) of 0.55 and 0.36 were investigated in this manuscript. Scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and pressure testing machine were used to determine the apparent morphology, micro-morphology, mass increase rate, flexural strength and compressive strength of cement-based materials containing dolomite powder. The sulfate resistance of mortars was improved with increasing dolomite powder dosage. Generally, the flexural strength and compressive strength of mortars in Na2SO4 solution were higher than those in water. Within 150 days of immersion, the corrosion resistance coefficient and compressive corrosion resistance coefficient of mortars increased with increasing dolomite powder dosage. The pore structure of cement-based materials became more compact with the addition of dolomite powder. Accordingly, the sulfate resistance was improved by controlling the dynamics stage due to the fact that the pore structure of cement-based materials was refined with the addition of dolomite powder. The 150-day compressive corrosion resistance coefficients of mortars with a w/b of 0.55 in the case of dolomite powder at 0 and 30 wt% replacement levels were less than 1, suggesting that long-term immersion in sulfate solution increased the deterioration rate of cement-based materials.