Abstract: The application of friction stir welding for avionics box packaging was studied. Rectangular track package welding of box cover and box body were successfully achieved by modified special 4-axis friction stir welding machine at a large spindle inclination. The surface morphology of the weld seam of specimens showed good and met the existing standard for gas tightness with no macro defects in every experiment. The maximum height deformation of the box varied from 1. 47 mm to 2. 53 mm. Experiments proved that the height deformation of the box decreased monotonously when welding speed increased; and it firstly decreased and then increased when welding rotation speed increased. Among the specimens,the two groups with smaller heat input suffered lower pressure limits as 0. 5-0. 6 MPa. Each of them enjoyed a tear-shaped opening located after at the first corner of the weld seam on the retreat side of the cylindrical stirring pin. Under the influences of pin shape,weld trajectory and welding heat input,the joint attained were with tiny holes,tunnels and other defects. These defects w Ere the reason for leaking by being expanded gradually under stress and pressure.