<p>We investigate theoretically a hydrogen sensor based on a one-dimensional core–shell nanoparticle chain. The nanoparticles are composed of silver cores coated with palladium (Pd) shells. The distance between adjacent particles is larger than three times the unit radius. This configuration allows for the analysis of the optical response of the designed structure using both coupled dipole theory (CD) and the finite-difference time-domain (FDTD) method. Leveraging the change in the dielectric constant of Pd before and after hydrogen absorption, combined with the collective effects of surface plasmons, the presence of H₂ is detected through differences in the absorption cross-sections. Results show that by constructing nanoparticle chain models with varying periods or particle sizes, Wood’s anomaly and ultra-narrow absorption cross-sections are observed both before and after H₂ absorption. Furthermore, the difference in the absorption cross-sections still exhibits Wood's anomaly and ultra-narrow absorption cross-sections. These effects are attributed to the long-range interactions between individual and collective interactions within the unit structures, which can be directly predicted by CD theory. The maximum of the difference absorption cross-sections would be reach to 16.7% when the concentrate of H₂ changes 4%. The occurrence of Wood's anomaly and ultra-narrow absorption peaks in the absorption spectral difference can effectively indicate the presence of hydrogen in the structure, thereby reflecting the characteristics of hydrogen sensing from another perspective.</p>