Abstract: Effect of lower temperature and high loading rate on the fracture behaviors of weld metal was studied.The results indicated that the fracture toughness reduces and the tendency to intergranular fracture increases with both reducing temperature and raising loading rate, which shows the low temperature effect and high loading rate effect and both of them promot each other.Intergranular fracture results from the inter action of metallurgical, structural and environmental factors.The tendency to intergranular fracture depended on the ability of grain boundary to suit with plastic deformation of adjacent grains.The intergranular brittle fracture will occur if the grain boundary can not suit with the plastic deformation.