Abstract: This study attempts to investigate the constitutive model and damage evolution law of the fiber-reinforced vegetation concrete substrate. Taking the two factors of confining pressure and fiber content into account, a statistical damage model that can reflect the mechanical properties of the substrate is established based on the Weibull distribution. The method for determining model parameters is given, and the relationship among the Weibull distribution parameters, the confining pressure and the fiber contents is discussed. The model is then used to verify the results of the triaxial tests on the substrate. According to the destruction criterion of the substrate, the method for determining the damage threshold is deduced. By analyzing the damage evolution characteristics and the failure process of the micro-element, the stress-strain relationship and the law of damage softening of the substrate are elaborated. The results show that the model curves agree well with the tests, which can reflect the damage softening characteristics during the loading process of the fiber-reinforced substrate. Besides, the ratio of the damage threshold to the peak strain is found to range from 0.4 to 0.6. This study provides a theoretical reference for the accurate analysis and evaluation of the mechanical properties of substrate.