Granulated blast furnace slag with volcanic ash charateristics can be used to produce slag-based cementitious materials after grinding. Compared with traditional cement, the hydration activity of slag-based cementitious materials is low. In order to enhance the hydration activity of grind granulated blast furnace slag （GGBS） in slag-based cementitious materials， this paper innovatively proposed to use polymerized aluminum sulfate solution to infiltrate and treat GGBS, accelerated the depolymerization of GGBS glass network structure, and improved the performance of slag-based cementitious materials. The ion dissolution behavior, surface elemental composition and microstructure morphology of GGBS-infiltrate were compared to GGBS-mix. The mechanism of infiltrated process to enhance the performance of slag-based cementitious materials was also analyzed by compressive strength, exothermic hydration, phase changes, and microscopic morphology tests. The results show that the amount of silicon ions dissolved in infiltrated filtrate is significantly higher than the amount of silicon ions dissolved in the mixed filtrate, the molar ratio of n(Ca)∶((n(Si)+n(Al)) on the surface of the GGBS-infiltrate is reduced to 0.266, and the structure of GGBS-infiltrate is corroded. The setting time of the slag-based cementitious material prepared using infiltrated GGBS is reduced to 147 min, and the compressive strength of samples reaches to 3.75 MPa at 1 d. The GGBS-infiltrated process can promote the generation of ettringite and C-A-S-H gel, accelerate the hydration process of slag-based cementitious materials, and improve the performance of slag-based cementitious materials.