To enhance the erosion resistance of steam curing high-ferrite Portland cement (HFC) elements and promote the application of HFC in marine engineering, the effects of slag (SL) and fly ash (FA) on the capillary pore structure and erosion resistance of HFC based materials were investigated under steam curing conditions at 50 ℃ by means of mechanical properties tests, capillary pore tests, chloride binding tests and X-ray diffraction. The results show that the incorporation of SL improves the early mechanical properties of steam curing HFC mortar due to its higher pozzolanic reactivity, while reduces the 28 d capillary porosity of HFC mortar. The significant reduction of the early mechanical properties of HFC mortar is attributed to the incorporation of FA, inducing a slow strength gain in the later stage, whereas the capillary porosity of HFC mortar also decreases owing to the “micro aggregate” effect of FA. The chloride binding results indicate that SL and FA promote the physical adsorption and chemical binding of chloride by cement, respectively. Both SL and FA improve the chloride binding capacity of HFC composite cementitious materials.