Abstract: Plastic flow machining (PFM) is a new process of severe plastic deformation (SPD).The aluminum sheets produced by PFM show obvious strain gradient along the thickness, and the grain sizeof them gradually changes from ultrafine grain on one side to coarse grain on the other.This kind of aluminum sheets with gradient structures have both high strength and high plasticity, which have a great application prospect.The die structure plays a crucial and even decisive role in the forming of gradient-structural sheetsproduced by PFM, but so far there is no few relevant research.In this paper, the control variates method is used to simulate the forming of aluminum sheets with gradient structures under different die structures by finite element method.The result shows that the lateral extrusion ratio x, the left equivalent strain ε_L and the right equivalent strain ε_R of the aluminum sheets with gradient structures are closely related to the value of the opening rounded cornerR and the extrusion angleCof the die, and x decreases with the increase of Rand C. In addition, when R is 1.5 mm and C is 120°, the difference between ε_R and ε_Lbecomes the largest.