Abstract: A new continuously heating method for hydrogen content determination was developed. The result of investigation on release process of residual hydrogen in HSLA steel metal and haz metal with this method indicated that residual hydrogen in weld metal exists in “strong” traps (cavities and inclusions) and “weak” traps (dislocations and grain boundaries), while residual hydrogen of HAZ metal exists mainly in “weak” traps. The release temperature of hydrogen in “weak” traps is lower. Attention should be paid to its effect on properties of welded joint.