Abstract: The effect of hydrogen content on the low temperature toughness of weld metalwas studiedby Nick-Breaktest, low temperature impact test and scanning electron microscopy test, which filled by self-shielded flux-coredwelding wire and held different periods in room temperature.The results show that all these conditions such as the high content of hydrogen in self-shielded flux-cored wire, uneasy outflow of hydrogen from the weld metal and the short-lived molten pool, make the content of hydrogen high in weld metal(immediately test after welding).The average value of impact absorbing energy at low temperature is low and the data are disperse under the action of hydrogen andnon-metallic inclusion. When the work piece stored40 days in room temperature, the content of hydrogen decreases, andthe fish eye decrease or disapear, and the average value of impact absorbing energy at low temperature increase and dispersion of the data decrease.