The invention discloses a vehicle tail skirt outer plate forming process. Before a sheet metal part as a blank is machined through a drawing process, a metal flowing guide gap is premachined in the edge of the sheet metal part for guiding metal to flow in the gap direction during drawing; the metal flowing guide gap is positioned on the edge of the maximum deformation position of a vehicle tail skirt outer plate; and then, the drawing process is used for forming. As the metal flowing guide gap is premachined in the vehicle tail skirt outer plate, the fluidity of the sheet metal part material in the machining process is improved, that is, the material is easier to flow in the gap direction during machining, the flowing resistance is reduced, the acting force can be reduced, and meanwhile, the noise caused by flowing resistance is eliminated.