Abstract: The effect of rare earth elements Nd and La on hydrogen permeation in pure iron was studied by means of a Davanathan apparatus Experimental results indicate the diffusion coefficient reduces as the amount of solute Nd or La increases. It's concluded that Nd or La is a reversible Shallow trap of hydrogen pemeation in iron The binding energy of hydrogen around solure Nd is 4.4 kcal/mol and the diffusion activation energy of hydrogen is 6.1 kcal/mol.