In this paper, the variation law and deterioration mechanism of fiber cement-based material properties during freeze-thaw cycles were explored. Mercury injection method was used to measure the pore characteristic parameters (total pore volume, total porosity, most probable pore size, critical pore size and average pore size) and the volume percentage (harmless pore, less harmful pore, harmful pore and multi-harmful pore) of fiber cement-based materials without freeze-thaw and after 300 freeze-thaw cycles. And the gray relative correlation degree was used to correlate the frost resistance index of fiber cement-based materials without freeze-thaw and after 300 freeze-thaw cycles with pore characteristic parameters and volume percentage respectively. The study shows that with the increase of the number of freeze-thaw cycles, the mass loss rate of fiber cement-based materials decreases gradually, that is, the mass increases gradually, and the compressive strength, dynamic elastic modulus and ultrasonic wave velocity all decrease to different degrees. The variation law of its internal pore characteristic parameters and volume percentage explain the microscopic reasons for the variation of the frost resistance index. After the freeze-thaw cycles, the relative correlation between the average pore size and pore volume percentage of fiber cement-based materials and the frost resistance index is significantly improved.