The loess with different thickness is in the humid-thermal coupling environment of rainfall-evaporation for a long period of time, which is very prone to induce the generation of cracks in the loess, significantly weakening the structural and integrity of the loess, thus affecting the construction of the project area. Therefore, it is necessary to study the effect of soil thickness on the cracking characteristics of loess under the action of wet dry cycles. In this paper, a series of indoor wet dry cycle tests were carried out to record the water content change and crack development of the specimens in real time, and the crack network was analyzed by using digital image processing technology combined with fractal dimension. The test results show that: the different evaporation paths and water contents lead to inconsistent water evaporation rate of the soil, and the greater the thickness of the loess, the slower its water evaporation rate; interfacial friction affects the cracking process of the soil, and the thicker the soil, the slower the development of cracks, and the lower the complexity of the crack network. As drying proceeds, the interfacial friction gradually decreases and the soil shrinks significantly. The dry-wet cycle effect will lead to the reassembly of soil particles, accelerate the water evaporation process, and the soil surface will deteriorate continuously. The results of the study can provide some guidance for the prevention and control of geologic hazards in the Loess Plateau region.