This paper deals with the dynamic failure elongation of mild steel, SGACD and advanced high strength steel sheets such as TRIP600, DP600 and TWIP steels. The failure elongation has been obtained from the high speed tensile testing machine with various strain rates ranged from 0.003/s to 200/s. The experimental result demonstrates that the tensile elongation does not simply decrease as the strain rate increases, but it decreases from the quasi-static state to the strain rate of 0.1 or 1/s and increases again up to the strain rate of 100/s. Furthermore, some high strength steels have the tendency that the tensile elongation increases as the strain rate increases. Moreover, the localized strain rate hardening in the necking region induces the increase of elongation.