Abstract: According to the shallow instability characteristics of channel expansive soil in cold and arid regions, the dry-wet and wet-dry freeze-thaw cycle tests of channel expansive soil in the north bank of Yili River are designed to simulate complex climate environment and direct shear tests under low stress conditions. The attenuation law of shear characteristics of channel expansive soil, such as shear strength, cohesion and internal friction angle, is discussed with the cyclic mode and dry density. The results show that with the increase in normal stress, the attenuation degree of shear strength decreases, and the decrease in dry density decreases the effect of shear strength deterioration. The attenuation rate of shear strength of samples after the initial wet-dry freeze-thaw cycle accounts for more than 40% of the total attenuation degree. After five cycles, the attenuation degree of cohesion of samples under the wet-dry freeze-thaw cycle is about 20% higher than that under the dry-wet cycle. Within a certain range of compaction, the greater the dry density of the sample is, the smaller the attenuation degree of cohesion and the greater the attenuation degree of internal friction Angle. The superposition of “squeezing” and “crack” effects should be taken into account when the increasing or decreasing law of shear strength index is analyzed. S1WDFT and S2WDFT are set as dangerous conditions in the initial construction and operation of the channel foundation soil, and the function of the variation of shear strength index with the number of wet-dry freeze-thaw cycles is fitted.