Industrial fiber crops are increasingly utilized in functional composites as substitutes for conventional fibers, aiming to address the limited microwave transmittance (MWT) and thermal conductivity (λ) of commercial glass fiber-reinforced composites (D-GFRC), which significantly reduce the service life of communication equipment shells and result in substantial waste pollution. Ramie fiber-reinforced composite (RFRC) possesses good dielectric/thermal management properties attributed to distinctive microstructure. However, the uncontrollable microstructure and unclear structure-property relationship of ramie fiber hinder its application in communication composites. Herein, the microstructures of ramie fiber, including aggregation and micro/nanopores structures, were successfully manipulated by coupling physical fields (temperature and force fields) with the guidance of molecular simulation. Subsequently, a clear relationship between microstructure and dielectric/thermal management properties was established. Moreover, leveraging this relationship, the performance of RFRC was optimized through coupled physical fields. Specifically, the MWT of RFRC reaches an impressive 95.9 %, and the λ is enhanced by 140 % compared to that of D-GFRC. Importantly, RFRC waste can be completely transformed into functional particles, thereby achieving a closed-loop utilization. This research strategy offers valuable insights into the regulation of microstructures and the development of recyclable wave-transparent composites derived from industrial crops.