Abstract: In order to explore the effect of microwave radiation on hard rock damage and reduce the difficulty of rock breakage, the granite rock was used as the research object. Rock porosity, ultrasonic wave velocity and rock tensile strength were used as indicators of damage. Rock damage under microwave irradiation was measured by the experimental method. The results show that the granite is not affected by microwave radiation within a certain range of microwave radiation power, and when the radiation power and radiation time reach a certain value, as the radiation power increases and the radiation time increases, the rock will be significantly degraded, manifesting as increased porosity, reduced tensile strength, and decreased ultrasonic wave velocity ; in the case of equal energy consumption, compared with low radiation power, long radiation time, high radiation power, short radiation time can cause more damage of the rock; water is an important factor causing rock damage, compared with the dry rock specimen, the change of the damage index of the saturated rock after microwave irradiation is more significant; the low-power, short-time microwave radiation energy makes the rock strength increase.