Based on electromagnetic flanging process of aluminum alloy sheet metal, numerical simulation was conducted to investigate the distribution characteristics of the electromagnetic force and the influence of geometry parameters on the electromagnetic force distribution, and then the influence of the electromagnetic force distribution on the forming quality of workpieces was revealed. The results show that in the process of electromagnetic flanging of aluminum alloy sheet metal, the marginal accumulation effect of the electromagnetic force was produced due to the existence of the precast hole. The aperture of the sheet metal and the inner diameter of the forming coil can affect the distribution of electromagnetic force by changing the ratio of the projection area to the coil area. With the decrease of the ratio of the projection area to the coil area, the marginal accumulation effect of the electromagnetic force becomes more prominent, and the electromagnetic force density of the hole edge increases. Materials in the corner area flow more significantly under the circumstance of the uniform electromagnetic force distribution, meanwhile higher forming height and smaller edge reduction rate can be obtained after forming, which means more uniform thickness distribution of the deformation area and better forming quality of workpiece.