Abstract: In order to explore the freeze-thaw damage law of granite-concrete composite in cold re⁃ gion environment，three kinds of granite-concrete composite with different interface roughness ( 0.61，1.18 and 1.69 mm) were designed. The rapid freeze-thaw machine was used to simulate different cold regions with 0，10，20 and 30 freeze-thaw cycles. The parameters such as appearance morphology change，mass loss，flexural strength loss，crack initiation toughness and fracture energy of granite-concrete composite after freeze-thaw were analyzed. The results show that with the increase of freezing and thawing times，the mass loss rate，longitudinal wave velocity attenuation and mechanical properties loss of the samples all show an increasing trend. After 30 freeze-thaw cycles，the longitudinal wave velocity of the sample with an interface roughness of 0.61 mm decreased by 13.03 %，and the flexural strength and fracture energy loss rates were 73.22 % and 67.67 %，respectively. The longitudinal wave velocity of the sample with the interface roughness of 1.18 mm decreased by 12.59 %，and the flexural strength and fracture energy loss rate were 61.28 % and 69.13 %. The longitudinal wave velocity of the sample with interface roughness of 1.69 mm decreased by 9.67 %，and the loss rates of flexural strength and fracture energy were 39.40 % and 41.97 %，respectively.The crack initiation toughness and damage factor of granite-concrete composite speci⁃ mens were calculated，and the linear fitting expressions of crack initiation toughness and freeze-thaw cycles under the above three interface roughness were obtained，it can provide certain references for related re⁃ search.

Key words: granite-concrete composites, freeze-thaw cycles, interface roughness, fracture toughness