The relationships between strength matching and diffusion hydrogen in weld metal were reviewed. The results show that the main sources of hydrogen in the welds of common welding methods are the moisture in welding consumables

impurities in groove and water vapor around arc. Among the influencing factors of hydrogen in weld

the GMAW method has the lowest diffusive hydrogen content

and the metallurgical reaction of hydrogen removal in arc depends on welding method

and the role of auxiliary hydrogen removal process can not be underestimated. When high strength steel is welded with low strength matching weld

the hydrogen-rich zone formed by HAZ is the weak link of the joint; when high strength matching weld is adopted

the hydrogen-rich zone of HAZ is not significant

but the hydrogen content in the weld is high

which becomes the weak link of the joint. The engineering applications of three kinds of relationships between strength matching and diffusion hydrogen in weld metal have achieved satisfactory engineering quality.In the welding of martensitic heat-resistant steel and its dissimilar steel

the innovative theory of high strength matching weld preventing HAZ from forming hydrogen-rich zone needs to be further studied.