Abstract: Granite powder (0%-32%) was used to replace part of cement clinker to prepare machine-made sand concrete. The isothermal calorimetry, mercury intrusion porosimetry as well as gas penetration testing-methods were employed to measure the hydration heat, pore structure, mechanical strength and gas permeability of the concrete. Combined with the gray-correlation analysis method, the relationship between gas permeability properties and pore-structure characteristics was established for concrete at various curing ages (28 days-130 days). The results show that appropriate granite powder added can slow down the hydration heat release rate, refine pore structure, increase compressive strength, and reduce gas permeability. The compressive strength value of the concrete with 8% granite powder is the highest while its gas permeability coefficient reaches the lowest. The gray-correlation analysis shows that the effective porosity and the pore with the size less than 100 nm play the most significant impact on gas permeability.