Abstract: Foreign-clay spraying is currently a common technology for ecological restoration of exposed rock slopes. However, under arid climate conditions, the large amount of internal water loss of the foreign-clay on the slope surface will easily cause shrinkage and cracking, which will affect the overall stability of the slope and the growth of surface vegetation. In this paper, aiming at the problem of cracking of the foreign-clay on the slope surface, by changing the thickness of the soil, polymer composite foreign-clay with different polyurethane (PU) concentrations is prepared to analyze the development characteristics of cracks through a series of indoor drying tests. In addition, particles (Pores) and cracks analysis system (PCAS) are used to conduct a quantitative analysis of the geometry of crack network, so as to further explore the influence of soil thickness and polymer additive concentration on fracture development.