Though investigating the mechanical properties of granite cooled by nature cooling (in air) and rapid cooling (in water) at the temperatures from 20to 800℃, the paper analyzed the failure mechanism of granite under various heating temperatures and cooling modes and discussed the effect of rapid cooling in water on residual mechanical properties of granite from longitudinal wave speed, stress-strain curve, uniaxial compressive strength, peak strain and Young''s modulus. The results show that the longitudinal wave speed, uniaxial compressive strength and Young''s modulus of granite decrease with the increase of temperature.The amount of decrement of them rapid cooled in water is more than that in nature air. The higher the temperature, the more severe the degradation of mechanical property is. The thermal shock generated by rapid cooling might exacerbates the deterioration of mechanical property of granite. The peak strain of granite under rapid cooling is less than that under natural cooling. The brittleness of granite is more obvious through rapid cooling in water than through natural cooling in air.