To address the “dead layer” effect in conventional 4H-SiC α-particle detectors, where thick metal Schottky electrodes (typically tens to hundreds of nanometers) induce energy loss in incident α particles and significantly degrade energy resolution, this study proposes an innovative design employing atomically thick graphene as both the Schottky contact electrode and entrance window to effectively suppress dead-layer energy loss and improve the detector's energy resolution. The investigation begins with SRIM simulations to assess the energy-loss characteristics of different electrode materials for 5.486 MeV α particles from a ²⁴¹Am source: for 100 nm-thick Ni and Au electrodes, energy losses at normal incidence are 38.36 keV and 43.50 keV, respectively, and increase sharply with incident angle; in contrast, graphene electrodes exhibit energy losses consistently below 0.04 keV. Subsequently, Geant4 simulations of α-particle energy deposition spectra under uniform incidence within a conical solid angle (half-angle 0-π/3) indicate that the dead-layer contributions from Ni and Au electrodes to energy resolution are 0.37% and 0.46%, respectively (representing 37% and 46% of the typical ~1% energy resolution for 4H-SiC α detectors), whereas graphene’s contribution is only 0.03%, thereby quantitatively confirming its capacity to substantially reduce energy-loss-induced spectral peak broadening. Experimentally, CVD-grown monolayer graphene was transferred onto the 4H-SiC epitaxial layer surface via a PMMA-assisted wet transfer process, yielding a graphene/4H-SiC Schottky α-detector prototype. Raman spectroscopy confirms successful high-quality graphene transfer, as evidenced by prominent G and 2D peaks; electrical testing demonstrates excellent rectification characteristics and low noise levels. Irradiation experiments with a 241Am α source in air produced a clear α energy spectrum peak near 5.4 MeV (after accounting for air-gap losses), achieving an energy resolution of 4.64% that closely matches the Geant4-simulated value of 4.22% and validating the composite spectral structure in which some α particles attain near-full energy deposition. The core innovation of this work resides in the integrated validation through SRIM/Geant4 simulations, device fabrication, and α-spectrum testing, which quantitatively elucidates the mechanism by which graphene electrodes suppress dead-layer energy loss and demonstrates their feasibility as ultrathin entrance-window Schottky electrodes for 4H-SiC α detectors. This research establishes a robust theoretical and experimental foundation for future development of high-energy-resolution graphene/4H-SiC α detectors in high-temperature and high-radiation environments, while providing new pathways for electrode optimization in wide-bandgap semiconductor radiation detectors.