This paper presents a multilayered composite structure consisting of silver cubes, dielectric gratings, dielectric layers, and metal films to precisely regulate the plasmonic characteristics of nanocomposite structures' surfaces. The electric field enhancement characteristics are investigated using the finite-difference time-domain method. The research findings indicate that increasing the grating period results in a redshift of the localized surface plasmon resonance peak. While an increase in grating thickness has a minor impact on the resonance peak position, it significantly enhances the resonance intensity. Effective coupling between localized and propagating surface plasmons is achieved when the relative permittivity of the dielectric layer ranges from 3 to 5, leading to a significant boost in electric field intensity. Furthermore, increasing the thickness of the dielectric layer weakens its coupling with the silver film and instead promotes high-intensity electric fields formation by local regions containing silver cubes. Therefore, optimizing both structural parameters and dielectric properties of the dielectric layer enables effective regulation of electromagnetic resonance effects in this composite structure, providing theoretical support for high-performance optical device applications.