Abstract: Hydrogen, as a clean energy source, plays a crucial role in fuel cells and industrial applications. However, its flammability makes the development of real-time, sensitive, and safe hydrogen detection technologies a key factor for expanding its applications. Traditional palladium (Pd)-based thin film sensors, due to their dense structure, have a relatively slow hydrogen diffusion rate and a long response time. To address this issue, this paper proposes the design of a hydrogen optical sensor based on a palladium nanoparticle superlattice thin film, which can be prepared by a self-assembly method to reduce costs. Compared with the traditional dense thin film system, the specific surface area of this palladium nanoparticle thin film can be as high as 1.2×10⁷ cm⁻¹, which is conducive to the rapid diffusion of hydrogen and is expected to improve the sensing response rate. In addition, the calculation results show that when hydrogen diffuses into the interior of palladium to form PdH_x, as the atomic ratio (x) of H/Pd increases from 0 to 1, the change in the transmittance intensity of the palladium nanoparticle superlattice thin film reaches 38%, which is significantly greater than that of the traditional dense thin film system, indicating higher sensitivity. This study provides a theoretical basis for the development of real-time and highly sensitive hydrogen sensors.