Hydrogen trapping behavior has been investigated by means of thermal desorption spectroscopy（TDS） for a high strength steel after it was tempered at the temperatures of 430 °C, 500 °C and 520 °C, respectively. The loss of ductility was characterized by slow strain rate test（SSRT） and microscopic observation. It shows that with hydrogen charging the fracture feature transfers from ductile to brittle, resulting in the loss of ductility. Undeformed microstructure immediately beneath the fracture surface in charged specimen corresponds to badly ductility compared to the obviously streamline plastic deformation in uncharged specimen. The activation energies for the peaks present in the TDS analysis are calculated for all tested steel and the activation energies for all temperature peaks are similar, corresponding to the similar types of hydrogen traps.
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