Abstract: In this paper, the cold crack lesistence of HAZ with four kinds of weld metals has bsen evaluated by using PRRC method. The mechanical behavior of the welded joint, the transformation and microstruclure in HAZ and the hydrogen diffusion in welded joints have bsen investigated systematically. The mechanisms by which different kinds of weld melals effect a change in the cold crack resistance in HAZ have been discussed, thus making a contribution to the researches on new welding materials with high crack resistance. Some new precautions against cold cracking have been suggested.