Because of light weight and great connectivity, the sheet metal frame is one of the most commonly structural parts. But due to its poor rigidity, deformation encouraged easily in assembly process. Based on finite element simulation, this paper establishes assembly analysis model of the sheet metal frame, and explores the influence of the deformation would happen on sheet metal frame when changing the fasteners’ order, the clearance between sheet metal frame and shin and the assembly process. It can be concluded that the gap between the sheet metal frame and the skin is an important factor affecting the assembly deformation of the sheet metal frame. By reducing the structural gap between the inner edge of the sheet metal frame, the gap between the outer skin and the outer edge of the sheet metal frame was reduced from 2.0 mm to less than 1.0 mm after positioning. At the same time, the method of first positioning the installation end face of the sheet metal frame, then positioning the web surface profile, and then tightening the sheet metal frame and skin is adopted. In the end, the sheet metal frame reduced the bulging deformation, ensuring the feasibility of assembly.