This paper aims to investigate the evolution law of soil cracks in the rainfall-evaporation process. Based on a full-scale slope model test

the surface moisture content of soil was measured

and the crack ratio was extracted by image vectorization technology. The critical water content during the repeated cracking process was studied by dividing the cracked soil into soil matrix and crack domains

respectively. The critical cracking matric suction and water content of the soil matrix domain were deduced and calculated according to the horizontal strain increment constitutive model of unsaturated soil. The results show that the soil cracking during the rainfall-evaporation process has repeatable characteristics

and the crack rate generally increases with the increase of rainfall-evaporation times; the cracking water content in the crack domains increases with the increase of rainfall-evaporation cycles

while the matrix domain has the opposite result. The matrix suction can both inhibit or promote the generation and propagation of the cracks. In the soil matrix domain

the cracking water content range calculated based on the constitutive model of the homogeneous isotropic unsaturated soil strain increment is close to the measured value

and the model can explain the variation law of cracking water content in soil matrix and crack domains.