Abstract: Dry ice particles are used as cooling media during welding with trailing intense cooling and sprayed from nozzle after they are mixed with compressed air. After dry ice particles contact with the sheet, they sublimate instantaneously while much heat is taken away, then the local area is cooled. Based on thermal elastic-plastic FEM (finite element method), the technology of 1561 aluminum welding with trailing intense cooling was simulated. After analyzing the effect of rectangular cooling source of different lengths and widths, the optimum rectangular cooling source was then achieved. Thus the design of the nozzle exit shape was guided to optimize the effect of welding with trailing intense cooling on stress and deformation.In this thesis, the optimum length and width are 40 mm×25 mm, the longitudinal residual tensile stress at the center of the plate decreases from 162 MPa to zero, and compressive stress on both sides from 59.3 MPa to 20.4 MPa, about 65.6%.