Abstract: In this paper,by means of the test method that combing the Hopkinson device of gas gun loading model with the measuring technique of Charpy V-notch specimen in gas gun device of split Hopkinson pressure bar,the dynamic toughness of welded joint and several factors affecting with high loading rate were studied.The results showed that the impact specimen has a special fracture apearance and the size of ductile fracture zone expressed the value of plastic deformation of crack.The value of parameters of fracture toughness of welded joint were affected seriously by some factors such as loading rate,matching strength and ambient humidity.The value of fracture toughness of heat affected zone represented the dynamic toughness of welded joint.