Taking Yunnan laterite as the research object, this paper studied the effects of different factors on the swell-shrink characteristics of Yunnan laterite and the influencing factors such as wetting-drying cycle time, wetting-drying cycle times and initial dry density were taken into account through the method of expansion and shrinkage test combined with image processing. The results showed that the expansion process of laterite can be divided into 3 stages: rapid expansion, slow expansion, and stable expansion. The contraction process could also be divided into 3 stages: slow contraction, rapid contraction, and stable contraction. With the increase of wetting time, the vertical expansion rate, moisture content, porosity and other expansive parameters of laterite increased as the “厂” type. The shrinkage parameters such as vertical shrinkage, transverse shrinkage, volume shrinkage and so on increased with the time of dewetting, showing the change of “S” type, and the moisture content and porosity decrease gradually. With the increase of humidification times, the stability of vertical expansion rate, the transverse expansion rate, and the volume expansion rate increased sharply first and then decreased slowly. With the increase of dehumidifying times, the vertical shrinkage, the transverse shrinkage, and the volume shrinkage increased firstly and then fluctuated slowly. With the increase of initial dry density, the vertical expansion rate, the vertical shrinkage rate, and the volume expansion rate increased, while the transverse expansion rate, transverse shrinkage rate, and volume shrinkage rate decreased.