In order to study the influence of friction on the thickness distribution of workpiece in superplastic forming,based on a TC4 deep cylinder with uniform side wall thickness achieved by direct-reverse superplastic forming,the influence of surface friction of preforming die and final forming die on thickness distribution was analyzed with MSC.MARC.Results show that increasing the friction coefficient of preforming die can efficiently reduce the thickness of the regions which need to be thinned,resulting in the final uniform thickness distribution along the component.Decreasing the friction coefficient of forming die can make the sheet tend to be integral formation,also resulting in uniform thickness distribution.According to the simulation results,the experiment on friction changing of direct-reverse superplastic forming was performed.The aerospace TC4 deep cylinder with uniform thickness of 1.50-1.78 mm was fabricated successfully.Compared to the thickness distribution of 1.18-2.24 mm of common direct-reverse superplastic forming,the thickness of friction changing is more uniform.