Under the control of drying-wetting cycle, taking the effects of initial dry density, wetting frequency and the number of drying, formation and evolution of crack of Yunnan laterite was studied by the combination of indoor experiment and image processing in this paper. The initial dry density was set at 1.20, 1.30, 1.40, 1.50 g/cm3, the change of crack was observed under drying-wetting cycles and expansion rate test method, characteristic parameters of cracks were extracted by Matlab image processing technology. The results show that the laterite samples were easier to crack when the initial dry density was higher under drying-wetting cycles; the laterite samples did not crack all the time when dry density of was smaller (1.20 g/cm3); the laterite samples cracked during the third wetting when the dry density increased to 1.30 or 1.40 g/cm3, the laterite samples crack in the second wetting when the dry density reached 1.50 g/cm3; The effect of the wetting process on the development of the laterite cracks was significantly greater than that of the drying process. The expansion rate of laterite samples increased with the time of immersion. The expansion was stable at dry density of 1.20, 1.30, 1.40 g/cm3 for about 8 min and about 36 min at dry density of 1.50 g/cm3. The number, length, area and width of cracks of laterite samples increased with the number of wetting and drying cycles. The number, length and area of cracks increased with the increase of dry density, and the crack width reached a peak at a dry density of about 1.30 g/cm3. The key factor of the laterite cracking caused by drying-wetting cycle was the inhomogeneous expansion of the laterite samples during the process of wetting, the laterite cracks were expanding cracks. The development process included cracks gestation period (0 to 2 times), cracks formation and development period (2 to 6 times) and cracks stabilization period (6 to 8 times), the result of these three stages finally affected the developmental trend of laterite cracks.