<p>With the rapid advancement of intelligent electromechanical systems and micro/nano engineering technologies, nanoscale magneto-electro-elastic phononic crystal (MEE-PC) plates have attracted significant attention in micro-/nano-acoustics and vibration control due to their superior elastic wave manipulation capability and flexible active tunability. Nevertheless, current research on bandgap characteristics of nanoscale MEE-PC plates still has limitations. The bandgap regulation mechanism involving nonlocal effects and multiphysical-field coupling remains unclear, and effective schemes for collaborative optimization of external field parameters are also lacking. To address these issues, the multiphysical-field-coupled wave governing equations are established based on Kirchhoff thin plate theory and Eringen’s nonlocal elasticity theory. The plane-wave expansion (PWE) method is subsequently employed to calculate the band structures of periodic MEE-PC plates. The effects of nonlocal parameters, prestress, magnetic potential, and applied voltage on the bandgap position and bandwidth are systematically investigated. Furthermore, a particle swarm optimization (PSO) algorithm is introduced to achieve coordinated optimization of multiple external physical-field parameters with the objective of maximizing the first bandgap width. The optimized parameter combination increases the first bandgap width from 17 to 81.2&#xa0;GHz, representing an enhancement of approximately five times. Sensitivity analysis and repeated independent experiments further confirm the robustness and reliability of the proposed optimization strategy. The results reveal that nonlocal effects play a critical role in the evolution of high-frequency bandgaps, while external multiphysical fields provide an efficient and flexible approach for active bandgap manipulation. This study provides theoretical guidance for the design and optimization of intelligent vibration-control systems and micro-/nano-acoustic devices.</p>