In order to study the influence of dry-wet cycles on the mechanical properties and microstructure of clay, a series of unconfined compressive strength tests and CT scanning tests were carried out to reveal the deterioration mechanism of clay caused by dry-wet cycles from macroscopic and microscopic perspectives. The following conclusions were drawn: With the increase of the times of dry-wet cycles, the compressive strength of clay maintained an exponential decline trend. After 4 cycles, the compressive strength lost about 40%, and after 8 cycles, the compressive strength basically reached the stable state. It can be seen that from the cross-section of CT scanning, during the dry-wet cycle, cracks start to develop around the sample and gradually expand inward. The width and length of cracks continue to increase, and the continuity also improves. With the increase of the times of dry-wet cycles, the porosity of each layer of the sample increased significantly and the porosity of the interface between different layers increased more significantly. The cracks between layers developed first, and vertical cracks also developed on the surface of sample. Besides, the number of connected pores increases while the number of isolated pores decreases. There is a negative exponential relationship between porosity and compressive strength of clay under different dry-wet cycles and when the number of dry-wet cycles reaches 4 times, the increase of porosity has less effect on the decrease of compressive strength.