The hydrogen embrittlement of a low carbon HSLA steel has been investigated by means of slow strain rate test (SSRT) on circumferentially notched specimens. Hydrogen was introduced into specimens by electrochemical charging and the diffusible hydrogen content was measured by thermal desorption spectrometry (TDS) analysis. The activation energy of hydrogen desorption in the present steel was calculated to be 12.75 kJ/mol after TDS analysis. The peak stress and displacement during notch tensile tests had been found to decrease simultaneously with diffusible hydrogen content, which could be expressed by two power law relationships, respectively. Fracture surface was a cleavage type indicating that the steel had high susceptibility of hydrogen embrittlement.