Abstract: Mechanical and deformation properties of perchlorinated soil are complicated under dry-wet cycles caused by the climatic environment, which threatens the safety of superstructures. In order to simulate the strength evolution process of soil from construction to service, natural perchlorinated saline soil in Qarhan Salt Lake region was selected and three compactness of soil samples with compaction were prepared to do wetting-drying test. Distilled water was added after each drying cycle to simulate the raining process. Unconfined compressive strength and shear strength were determined during dry-wet cycles. Microstructural changes during dry-wet cycles were observed to reveal the changing mechanism of soil mechanical properties. Experiments show that the unconfined compressive strength of soil samples is increased by 128.3%, 138.9%, and 231.9%, and reaches the peak values at the 5 dry-wet cycles. Meanwhile, the cohesion c is also increased by 200.0%, 215.7%, and 197.2%. When the soil samples undergo 6~12 dry-wet cycles, the strength of the soil samples first decreases and then tends to be basically stable. Microstructural observation indicates that the amount of bond materials among particles nearly shows the same change tendency with soil strength. Results indicate that the strength of perchlorinated soil increases at the early stage and then decreases with the increase of dry-wet cycles, which is mainly caused by the changes in microstructures. More attention should be paid to the drainage of rainwater on the ground surface of perchlorinated soil after the construction process.