In order to study the qualified support spacing of flow drill screwdriving fixture,6k21 and 6061 aluminum alloy plates were taken as the research objects,and the deformation of different thickness plates with different support spacing under three different situations were test,such as no clamping point at both ends of 100 mm × 40 mm plate,having clamping point at both ends of 100 mm × 40 mm plate and no clamping point at both ends of 300 mm × 120 mm plate.Mechanical tests were carried out to verify the relationship between mechanical properties and plate deformation.The test results show that the mechanical properties of the plate will decrease with the increase of the deformation;the plate deformation can be reduced by setting the clamping point and increasing the size of plate;for small-size panels,if the support spacing is greater than 40 mm,clamping points should be added;the maximum support spacing of large-size plate can be set to 80 mm without setting clamping points.The test results can provide reference for fixture design of flow drill screwdriving panel.