To study the law of clay evaporation cracking, the evaporation cracking tests of plain soil samples; xanthan gum, guar gum and their 1∶1 mixed gum composite clay samples were carried out to explore the changes of water content and evaporation rate of different types of biological glue composite clay samples with time, and the characteristics of the fracture rate and fracture development morphology of the sample with the change of water content. The microstructure and mechanism of the composite clay samples were further analyzed by scanning electron microscopy. The results show that the evaporation process of soil sample experienced the loss of surface free water, internal free water and weak bound water, while the evaporation rate gradually decreased. During the process of evaporation, the formation of cracks reduces the water migration path, and the entry of air reduces the permeability coefficient of the sample, and the interaction between them makes the evaporation rate dynamic equilibrium. When the force between soil particles is balanced, the cracks no longer develop and the evaporation rate gradually decreases. The anti-cracking ability of the sample was enhanced and the crack development was wea-kened by the incorporation of biological glue.