Abstract: To address the challenge of comprehensively and efficiently investigating the evolution of mechanical properties of glass fiber reinforced polymer (GFRP) laminate in complex wind-sand environments solely through physical testing, a numerical model for the mechanical property evolution of GFRP laminate under wind-sand erosion was developed. This model integrates the Discrete Element Method (DEM) within ABAQUS with a user-defined VUMAT subroutine. Initially, the effectiveness of the model for simulating composite mechanical properties was validated through fiber-direction tensile tests on uneroded GFRP laminate. Subsequently, the accuracy of the model was verified using wind-sand erosion test results under varying erosion velocities, and the predictive accuracy and generalization capability of the model were confirmed through supplementary tests under different sand flow rate conditions. The results demonstrate that, in the fiber-direction tensile tests, the simulated tensile strength and elastic modulus agree well with the experimental values, yielding relative errors of 1.2% and 2.8%, respectively. Under varying erosion velocity conditions, the relative errors between the simulated and experimental values for tensile strength and elastic modulus range from 0.51% to 3.59% and 0.84% to 4.62%, respectively. Under different sand flow rate conditions, the model predictions exhibit high consistency with the experimental results, with relative error ranges of 0.01%–1.09% and 0.41%–4.89%, respectively. Additionally, the simulated damage morphologies of the GFRP laminate align consistently with the experimental observations across the various erosion velocities and sand flow rates. In conclusion, the established numerical model demonstrates high precision and excellent predictive capability, making it a reliable tool for evaluating the mechanical property degradation laws and damage evolution behavior of GFRP laminate under normal impact erosion conditions.