Metakaolin composite grouting material is an inorganic grouting material mixed with a large proportion of metakaolin in cement, which is used for anti-seepage grouting engineering of rock fissures in grottoes. In this paper, the hydration and product characterization of binary and ternary metakaolin composite grouting material were studied by means of hydration heat, XRD, FTIR, and SEM-EDX test. The feasibility of applying this material to grotto fissure grouting was analyzed by mechanical properties and water-solube salt test. The results indicate that the reaction degree of cement materials with is low. But the dilution effect and pozzolanic reaction of metakaolin and the charge compensation effect of active Al have a significant advantage in reducing the salt and alkali content in leaching solution. The addition of silica fume can enhance the hydration degree and mechanical strength of ternary composite grouting material. However, the decrease in Al/Si of hydrated products is not conducive to the adsorption of K+ and Na+. The metakaolin composite grouting material is a safer material than ordinary Portland cement in grotto protection, and it exhibits better compatibility with grottoes environment. Additionally, metakaolin, as a supplementary cementitious material, has more advantages over silica fume in reducing K+ and Na+ leaching.