As a new type of directed-energy weapon, high-energy laser (HEL) systems demonstrate significant advantages in counter-unmanned aerial vehicle (C-UAV) operations, including rapid response and high cost-effectiveness. Taking the small quadcopter as a typical research subject to conduct modeling, simulation, and quantitative analysis of HEL damage effects. Firstly, the research status of C-UAV technologies was systematically reviewed. Subsequently, a damage assessment model was established, incorporating key modules such as laser atmospheric transmission, irradiation response calculation, and damage degree evaluation. Through vulnerability analysis of UAV systems, critical damage components were identified, enabling the development of a thermo-mechanical coupled laser damage assessment model. Finally, numerical simulations were performed to evaluate damage effectiveness under various operational parameters. The simulation results demonstrate that the damage time exhibits strong correlations with both engagement distance and laser power density. Specifically, the damage time increases with reduced operational range and increased power density.