Abstract: In order to study the meso-structural evolution of expansive soil during wetting-drying cycles, the CT-consolidation apparatus was developed; A number of tests of wetting-drying cycles were carried out for intact and remolded expansive soil under loading condition, and CT scanning was taken on samples after each wetting and drying finished.The research results indicate that during wetting-drying cycles the amount of shrinkage and swell of samples are large. After three times of wetting-drying cycles, the volume of soil samples under the same saturation is no longer changed. Both wetting and drying can induce the structural damage of expansive soil samples. After first drying, cracks generate on expansive soil samples obviously. Along with the experiment, cracks continue to expand, soil damage accumulate. The upper load has some inhibitory effect on the crack development and influences the development of the crack and the shape of the crack-network. The crack of undisturbed expansive soil is developed around the first formation of main crack while remolded expansive soils crack is a turtleback. The CT data M_E of samples are bigger in saturation of 85% than in saturation of 25%. TheCT data M_E of samples in both wet and dry states are all approximately linear with the number of wetting-drying cycles and the slope of the former is relatively flat, while the latter is steeper. Meso-structural evolution parameters are defined, and the relationship between meso-structural evolution parameters and saturation, wetting-drying cycle times is proposed, the predicted results are close to the experimental data.