In this paper, based on the simple use of volcanic ash material to modify slaked lime, the ash is loaded with nano-SiO2 to further modify the mortar. The obtained modified mortar has a shorter curing time, improved mechanical properties and good water resistance. The X-ray diffractometer (XRD), thermogravimetric analyzer (TG) and scanning electron microscope (SEM) were used to analyze the modification mechanism of the material. The results show that the presence of volcanic ash material caused the volcanic ash reaction and carbonation reaction to occur simultaneously in the solidification process of the slaked lime, and the C-S-H generated by the volcanic ash reaction effectively improved the mechanical properties of the mortar. The loaded nano-SiO2 acted to fill and promote the pozzolanic reaction to achieve further modification.