Abstract <p>This article presents a high-absorption terahertz material based on a graphene-quartz composite coating and establishes a simulation model with experimental validation. A simulation analysis of the composite coating was conducted by adjusting the particle size of the embedded quartz sand to modify the surface roughness. The coating design parameters were optimized to build the unit model, and coating samples were prepared for absorption rate measurement. The simulation results showed that the coating exhibited excellent absorption in the 0.1–0.3 THz range, while experimental results confirmed an absorption efficiency exceeding 97.20% within the 0.14–0.22 THz range. The analysis yielded a coefficient of determination (<i>R</i>²) of 0.81, indicating a good fit between the simulation model and experimental data. This model predicts the absorption characteristics of a graphene-quartz sand composite coating in the terahertz band, providing a theoretical basis for the design of future terahertz wave-absorbing materials and the development of thermoelectric terahertz power detectors.</p> Graphical abstract <p></p>