The deformation caused by uneven heating in welding technology is always a difficult problem in industrial production. At present,for the problems of welding residual stress and deformation,ultrasonic impact technology has achieved a good results in many methods. The deformation resistance of the material reduces when the temperature is high. Based on this,a front trailing ultrasonic impact test platform is built. The front trailing ultrasonic impact test of 3 mm Q235 B sheet is carried out. The relationship between the welding deformation and grain change at the weld and the impact distance is mainly explored. When d =45 mm the deformation is reduced by 43.3% comparing with that of conventional welding, that is the effect of deformation reduction is most obvious when high temperature impact occurs. At the same time,it is found that the grain refinement of the weld is most obvious when the impact distance is short.