The influence on mechanical properties, phase composition, microstructure of cement slurry with granite powder (GP) as a mineral material was conducted by using X-ray diffractometer (XRD), scanning electron microscope (SEM), synchronous thermal analyzer (TG-DSC). The results show that under standard curing condition, the compressive strength of cement slurry containing 15% (mass fraction, the same below) GP curing for 28 d reaches 37.0 MPa, which is highest value. The linear shrinkage of cement slurry with 10% GP curing for 56 d decreases by 18.3% than that of cement slurry without adding GP. The initial setting time and final setting time of cement slurry containing 20% GP are shortened by 207%, 18.2%, respectively. The flexural strength of cement slurry with 20% GP curing in water for 28 d is 48% higher than that under standard curing. GP participates in the hydration process of cement slurry through pozzolanic effect to form more hydrated calcium silicate (C-S-H). Adding GP can promote the formation of type I C-S-H in cement slurry, which is beneficial to improve the mechanical properties and shorten the setting time of cement slurry.