The high-strength low-alloy( HSLA ) steel heat-affected zone (HAZ)softening was predicted using a grey model.HSLA steel DILLIMAX690E,NK-HITEN610U2 and BHW35 were taken as examples in the research on ultra-narrow gap automatic welding technology. Test results turned out to be that the errors between the values calculated by the Grey Model (GM) (1,1)model and their actual value were less than 2％,indicating that the grey prediction method could accurately reflect the actual situation of the high-strength low-alloy steel heat-affected zone softening.This method will play a crucial role in guiding the applications of HSLA steel welded structures in the future.