The invention discloses a self-positioning strip reinforcing rib forming device. The device is characterized by comprising an upper die assembly and a lower die assembly; the upper die assembly includes an upper die frame, an upper base plate, an upper fixed plate and a pressure plate; the lower die assembly includes a lower die plate, a lower base plate and a lower die frame; limiting projections are arranged around a strip by one lap on the pressure plate, and include a first connecting part and a second connecting part; and the second connecting part is distributed in a horn shape. By adoption of the abovementioned structure, a lower die insert and an upper die punch are utilized to perform punch forming on the strip part, and a spherical projection and a forming groove are utilized to form a reinforcing rib of the strip. In order to perform self-guide positioning on the strip, the pressure plate is provided with the limiting projections arranged around the strip by one lap, and the limiting projections include the first connecting part and the second connecting part; and as the second connecting part is distributed in a horn shape, the gradual self-guidance can be performed.