Abstract: The hydrogen adsorption and diffusion mechanisms at zirconium surfaces and bulk phases were systematically investigated through first-principles calculations to address unresolved questions regarding atomic-scale hydrogen interactions. The study focused on four critical stages of hydrogen incorporation: molecular dissociation, surface adsorption, interfacial diffusion/penetration, and bulk-phase diffusion. Energy barriers along specific diffusion pathways were calculated using the climbing-image nudged elastic band (CI-NEB) method, with temperature-dependent diffusion coefficients derived for each pathway. Computational results revealed a dissociation barrier of 0.07 eV for hydrogen molecules at surface sites, followed by preferential adsorption of atomic hydrogen at hexagonal close-packed (hcp) sites. Subsequent energy barriers were quantified as 0.31 eV for hcp → face-centered cubic (fcc) surface diffusion, 0.85 eV for fcc surface → subsurface octahedral site penetration, and 0.43 eV for tetrahedral → octahedral site transitions in bulk zirconium. Comparative analysis identified the surface-to-subsurface transition as the rate-limiting step governing hydrogen absorption kinetics. This study provided atomic-scale insights into hydrogen permeation mechanisms in zirconium-based systems, serving as a theoretical foundation for optimizing getter materials and mitigating hydrogen embrittlement in nuclear reactor cladding applications.