Abstract: The number of exposed rock slopes gradually increases with the scale and number of infrastructure construction. As an effective slope protection and greening technology,guest soil spraying technology can enhance the surface stability of rock slopes. However,various factors contribute to water loss and cracking of the surface soil,which can impact the repair effectiveness of guest soil spraying. To address this issue,sisal fiber and polyacrylamide(PAM) are utilized to enhance the external soil in this paper. Dry shrinkage cracking tests were conducted under different conditions,including varying thickness,sisal fiber content,and polyacrylamide(PAM)content. The effects of these different conditions on soil drying,water loss,and surface crack development were studied. The internal structural changes of the improved external soil were discussed and analyzed using scanning electron microscopy(SEM). The results indicate that,with the increase in soil layer thickness,the evaporation stability time of the improved soil is prolonged,effectively inhibiting the development of surface cracks. The addition of sisal fiber and PAM extends the evaporation path of clay,leading to a gradual decrease in the evaporation rate of the soil with an increase in fiber and PAM content. This improvement also hinders the development of surface cracks in the soil. The strong water absorption capability of PAM contributes to reducing the soil's evaporation rate,while the bridging effect of fiber inhibits the expansion of cracks,enhancing the overall integrity of the soil.