Abstract: The pirtial atom strain field of hydrogen in α-Fe was measured and the variation of the strain components with the hydrogen concentration was investigated. The strain components ε₁ and ε₂ under Boltzmann distri bution are calculated.Hydrogen permeation measurements under tensile and compressive stress were carried out using a special device designed by ourselves, which can easily apply a same tensile and compressive load to a cross specimens.The results show that ε₁> 0, ε₂<0, i.e. the partial strain field of hydrogen in α-Fe has an intensive tetragonal distortion. The experiment shows also that the apparent strain components decrease with increasing hydrogen concentration.