In order to obtain the pore characteristics and permeability change law of water-quenched granite subjected to different temperatures, the water-quenched granites from 20 ℃ to 600 ℃ were used as the research object. Pore structure characteristics of the samples were tested by mercury intrusion porosimetry and permeability of the samples were measured by the transient pulse attenuation method. And the measured permeability was compared with the calculated value which was predicted based on the K-T model. The following conclusions were obtained: with temperature increasing, the porosity and permeability of water-quenched granite increased exponentially. 500~600 ℃ was the threshold temperature range for the change of porosity and permeability of water-quenched granite. Most of the new pores in the granite induced by high temperature and water quenching were mesopores. The significant increase of the porosity and permeability of water-quenched granite can be attributed to the growth of the mesopore content. The predicted permeability based on the K-T model can reflect quite well the variation trend of the true permeability. The research results can provide reference for the design and construction of high-temperature geothermal development projects.