Abstract: The displacement behavior of hydrogen deuterium between gaseous phase and Pd hydride particles has been studied. The experimental results show that the optium effect can be attained with gas linear velocities between 2.0 cm/s and 8.5 cm/s at room temperature(≈22℃) for finer particles(≈0.15 mm) and the apparent reaction is affected mainly by the chemical reaction rate at the gas solid interface.The displacement performance has little change as temperature increases from 22℃ to 75℃ and the process is much slower at the temperature lower than 10℃ because of the lower hydrogen deuterium atom diffusion in solid phase.