Abstract: In order to develop a new type of green high-performance mine grouting material, ordinary Portland cement (OPC) and fly ash (FA) were used as raw materials, and fly ash-cement-based grouting material (FCGM) was modified by introducing nano-silica (NS) to construct a high-performance composite grouting material system. The effects of NS on the properties, mechanical properties and evolution of hydration products of FCGM slurry were systematically studied by different macroscopic and microscopic test methods. Through the grouting consolidation test of sandstone aggregate, the influence of NS modification on the macroscopic mechanical behavior and acoustic emission (AE) damage evolution characteristics of the cement was compared and analyzed. The results show that the content of NS has a significant effect on FCGM, which can significantly improve the compressive strength of FCGM, shorten the setting time, reduce the bleeding rate and reduce the fluidity. Especially when the NS content is 1%, the compressive strength of FCGM is the best, and the compressive strength of 3 d and 90 d is 49.6% and 98.00% higher than that of the control group N1, respectively. Microscopic characterization (XRD, FTIR, TG-DTG and SEM) confirmed that NS could effectively promote the hydration process of FCGM and significantly optimize the internal microstructure of the stone body. The grouting reinforcement test of sandstone shows that the 28 d uniaxial compressive strength of 1% NS modified FCGM consolidated body is increased by 90.8%, and the crack propagation and pore development are effectively inhibited, and its multifractal characteristics are improved. The AE monitoring further reveals the NS enhancement mechanism. The damage precursor signal of the modified cement is earlier and more active, which shows the synchronous rapid growth of high amplitude ringing count and cumulative energy, and finally changes its macroscopic failure mode from tension-shear composite to tension-dominant. By establishing the multi-scale correlation between material modification, microstructure, macroscopic mechanics and damage evolution, the comprehensive mechanism of NS reinforced FCGM is clarified, which provides theoretical basis and data support for the development of high-performance deep grouting materials and the prediction of their engineering failure behavior.