A method of cutting an organic light-emitting display panel substrate into OLED display panels is disclosed. In one aspect, the method includes forming a plurality of OLEDs over a lower mother substrate, wherein the OLEDs are divided into a plurality of groups. The method also includes forming a plurality of sealant lines over at least one of an upper mother substrate or the lower mother substrate such that each sealant line surrounds a corresponding group of the OLEDs. The method further includes forming a plurality of assistance sealant lines between adjacent sealant lines, attaching the upper mother substrate to the lower mother substrate with the sealant lines and the assistance sealant lines interposed therebetween, and cutting the upper mother substrate and the lower mother substrate along the assistance sealant lines.