Abstract: Fly ash generated during the development of coal resources seriously occupies land and pollutes the environment, and its recycling is of great significance to the protection of the ecological environment and the improvement of social and economic benefits. In order to study the influence of fly ash grouting material and alkali activator content on grouting effect of fractured rock mass, cement grout with different contents of fly ash (0%, 10%, 20%, 30%) and sodium silicate (0%, 1%, 2%, 3%) was prepared and injected into through cracks of rock mass with prefabricated cracks at different angles. The wave velocity of the junction entity is tested. The results show that when the content of sodium silicate is less than 1%, the wave velocity increases slightly with the increase of crack angle, but it is not significant, and there is no obvious change with the increase of fly ash, indicating that the content of sodium silicate is too small to completely react with fly ash. When the content of sodium silicate is 2%, the wave velocity decreases significantly with the increase of sodium silicate, indicating that fly ash and sodium silicate fully react to form geopolymers through the polycondensation process. These polymers fill the voids between particles, reduce the connectivity of pores, and result in fewer internal cracks, dense structure, and significantly reduced wave velocity. When sodium silicate content is 3%, excessive sodium silicate will form inorganic foam, hinder the reaction process, resulting in a decrease in the formation of geopolymer, an increase in the space between particles, an increase in porosity, and thus an increase in wave velocity. The research results provide a certain reference for the work of fly ash and sodium silicate in grouting.