Abstract: A new method of welding with trailing gas fluid field to control flexibly unstable deformation of high-strength aluminum alloy 2A12 thin plate, and the feasibility was analyzed. The influence of high-speed gas fluid load on the welding stress evolution law of the thin plate was studied. The mechanism of controlling of welding residual stress and deformation was illustrated. Based on the finite element method, the temperature field and stress field were analyzed to determine the distance between aerodynamic load and heat source, which was the key factor, obtaining the reasonable and effective range of gas pressure. Welding experiments were conducted using a self-developed device. The results show that when the distance between aerodynamic load and heat source is 20 mm and the gas pressure is 30 MPa, the welding instability deformation is basically eliminated . The longitudinal residual tensile stress peak value on the cross section of the weld seam decreases by 77.73% compared to conventional welding, and the residual compressive stress peak value decreases by 69.23%. The maximum deflection of the plate edge deformation is only 0.9 mm, which is a drop of 89.41% compared to 8.5 mm of conventional welding. The experimental results are in good agreement with the simulation results.