Abstract: For the expansive rock in the Nanning basin, its expansibility, shear strength and thermal characteristics are measured by using, respectively, the undisturbed samples and the remolded samples of different particle sizes in the laboratory test, and the differences of their values are studied. The results show that the free swelling ratio of the remolded expansive soil samples in different particle size ranges sees a significant increase, as compared with undisturbed ones, but the peak value of the principle stress difference, the shear strength and the thermal characteristic index are decreased. Therefore, the soil particles of appropriate sizes should be selected for remolding instead of undisturbed samples in the laboratory test. The free swelling ratio and the expansive force of the remolded samples take similar values as with the undisturbed samples when the soil particle size is in the range of 1 mm≤d<2 mm and the properties of samples in the minimum range of the soil particle size are close to those of the undisturbed samples, as shown in the triaxial test and the thermophysical experiment.