The influence of hydrogen (H2) loading on optical and surface characteristics of nanometric palladium films was studied. Pd films were deposited on silicon substrates by electroless method. H2 loading was realized by annealing the Pd films in H2 atmosphere at 585 Torr over the temperature range of 200-500°C. Pd films with initial thickness under 40 nm were chosen to observe incomplete covering effects. Refractive index measurement was used to monitor the H2 loading. Changes on refractive index and surface morphology are related to the existence of a and b phases in Pd-H system.