Abstract: Mid-infrared absorbers, offering distinct advantages including high specificity, high sensitivity, non-destructive testing capability, and quantitative analysis, are recognized as valuable components in a wide range of applications such as thermal radiation sources, thermal imaging, infrared detection, and gas sensing. A cylindrical stacked metal-dielectric-metal (MDM) resonator structure was designed using high-temperature-resistant materials, tungsten (W) and silicon dioxide (SiO₂), with the aim of achieving high-performance broadband absorption in the mid-wave infrared region. Through electromagnetic simulation and structural optimization, cylindrical resonators of varying dimensions were found to correspond to different absorption peaks within the 3 μm~5 μm wavelength range. The observed multi-peak absorption characteristics were attributed to the size-dependent frequency shift of localized surface plasmon resonance (LSPR) modes excited in distinct MDM cavities. Furthermore, by integrating four resonators with different diameters into a multi-size composite unit cell, an average absorptivity of 86.9% was achieved across the 3 μm~5 μm broadband spectrum, and the structure was demonstrated to be insensitive to both TM- and TE-polarized incident light. The proposed absorber shows promising application potential in thermal management, infrared stealth, and sensing detection.