Abstract: In order to study the effects of different freezing and thawing methods on the fracture toughness of concrete with double-K, five groups of 15 specimens, respectively subjected to drying, water immersion, freezing and thawing, salt immersion and salt freezing and thawing for 20 days, were studied in the three point bend test. The eigenvalues and the whole process curve of the load, the displacement of the mouth and the strain at the tip of the crack were measured. Based on the double-K fracture theory, the effective crack length, the crack initiation load, the instability load and other fracture parameters were calculated. The results show that the influence of different freezing and thawing methods on the concrete has some similarity. Not only the concrete of water freezing and thawing but also the concrete of salt freezing and thawing can damage the elastic modulus of the concrete, decrease the mechanical properties of the concrete and increase the toughness of the concrete. However, there is a significant difference in the way of freezing and thawing between the degree of damage and the concrete after damage. Water freezing and thawing damage to the concrete is mainly manifested in the fact that the concrete is more easily cracked when subjected to water freezing and thawing, but the effect of water freezing and thawing environment on the development of concrete in resistance to cracking is insignificant. Salt freeze-thaw damage to concrete is mainly manifested in the salt freeze-thaw resistance to concrete cracks and the development of the ability to reduce at the same time, but the concrete cracks occurrence will be relatively postponed.