Abstract: Cementing materials are one of the main factors affecting the compressive strength and the cost of cemented tailings backfill (CTB). The evolution of compressive strength of CTB with different curing time was investigated using two kinds of cementing materials, including cement and cementing powder (slag-based). Besides, a comprehensive comparative analysis of the mechanism for generating differentiation in compressive strength of CTB was carried out at the microscopic level by combining the chemical binding water test, XRD, SEM and MIP testing methods. The results showed that the early and long-term compressive strengths of the slag-based CTBs (SBCTB) were significantly better than those of the cement-based CTBs (CBCTB). On the one hand, the total amount of hydration products in SBCTB, particularly ettringite was higher than that in CBCTB. On the other hand, the internal hydrated calcium silicate of SBCTB had better micro-mechanical properties, and its combination with ettringite strengthened the connection between the hydrated calcium silicate, and further filled and refined the internal pore structure of the SBCTB, and improved the overall compactness of the SBCTB, all of which enhanced the compressive strength of the SBCTB.