The current study reports influence of addingdolomite powder (DP) as partial replacement ofground granulated blast furnace slag (slag) on performance of slag-cement self-compacting mortar (SCM). The SCM with a typical slag-cement bindercomprisedofequivalentmassratioofordinaryPortlandcement(OPC)toslagwasusedasthe reference mixture. The effect of DP on performance of the modified SCMs was accessed by using various DP to slag ratios while fixing OPC amount at 50% in mass of total powder. Experimental results showed that DP addition substituting slag enhanced workability of the modified SCMs. Increase of DP addition induced the modified slag-cement pastes with slightly decreases in both peak of hydration heat liberation and cumulative hydration heat released during 24h. With ages of curing earlier than 3 days, DP addition decreased the compressive strengths of the modified SCMs. After 7 days of curing, the SCMs with DP addition up to 30 mass.% replacing slag had the highest compressive strengths. Analysis on particles size distributions of the SCMs showed that the DP addition in range of 30–50 mass.% substituting slag could be the optimum amount for improving microstructure of the hardened mortars.