This study investigated the influence of C-F-S-H/PCE (calcium-ferrite-silicate-hydrates/polycarboxylate ether) nanocomposites on the hydration and compressive strength of slag cement. Various methods including mechanical property testing, isothermal calorimetry, X-ray diffraction analysis, and mercury intrusion porosimeter were employed to investigate the compressive strength, hydration, and microstructure of the cement blended with various slag levels (i.e., 50 wt.%, 70 wt.%, 90 wt.%). The results revealed that the C-F-S-H/PCE nanocomposites significantly enhanced the strength development of slag blended cement. The 1-day compressive strength of 50% slag-cement got increased by 60%. The main reason for this was the regulatory effect of C-F-S-H/PCE nanocomposites on the hydration reaction of slag blended cement. By accelerating the early hydration of cement and the formation of calcium hydroxide, the reactivity of the slag was stimulated, thus promoting its continuous reaction.