To explore the mechanism of phosphogypsum in modification of grouting materials for mines, grouting materials were prepared with different proportion of ingredients. Performance indicators including fluidity, permeability, strength parameters and leaching rates of heavy metals were analyzed, and the microscopic mechanism of phosphogypsum-modified grouting material was also explored with scanning electron microscopy and X-ray diffraction. Results show that an addition of phosphogypsum in grouting materials can not only actualize effective utilization of resource, but also improve fluidity of grouting material. It is shown that by adding 30% of phosphogypsum, the grouting material exhibits better fluidity and impermeability, significantly enhanced compressive and flexural strength, and reduced leaching rates of heavy metals. Furthermore, phosphogypsum can promote secondary hydration reaction, leading to more calcium-silicate-hydrate gel, which thereby can improve structural stability and engineering performance of grouting material.