Abstract: Expansive soil, a special type of soil rich in montmorillonite, illite and other hygroscopic minerals, exhibits significant shrink-swell properties, fissuring behavior and overconsolidation. Under wetting-drying cycles, the crack development in expansive soil is pronounced, and its shrink-swell behavior threatens the stability of geotechnical engineering structures. In this study, CT scanning technology and a self-designed humidification-swelling apparatus are used to investigate the crack development patterns and their impact on the lateral swelling pressure of expansive soil under different numbers of wetting-drying cycles. The results show that the development of lateral swelling pressure in expansive soil exhibited a three-stage development characteristic, namely rapid growth, slow growth and stabilization. The increase in the number of wetting-drying cycles significantly reduces the soil's expansiveness, leading to a rapid decrease in the peak lateral swelling pressure. The depth and connectivity of cracks increase with the number of wetting-drying cycles, providing preferential seepage pathways for water infiltration and accelerating the soil's swelling deformation. The research results provide a scientific basis for engineering construction in expansive soil regions and help prevent geotechnical disasters such as landslides and slope instability caused by wetting-drying cycles.