Abstract: The Plate Rigid Restraint Cracking tests(PRRC) have been used to study the welding cold cracking suseeptibilities of four kinds of domestic HSLA steels in this paper.And the effects of diffusive hydrogen content in welded joint,welding heat input,local preheat tempreture, restraint intensity and addional stress induced by local preheating on cold cracking susceptibility of steels have been discussed.On the basis of above research,the critical cooling time criterion t_cr of domestic HSLA steels is established.This criterion is proved to be reliable by real application,and hasimportant significance to assess if cold cracking occurs under conditions of weldingprocess in operation and to determine reasonable welding process.