Abstract: The microstructure and mechanical properties of a Cu-containing high-strength steel for oil storage tank were investigated by using optical microscopy, scanning electron microscopy, transmission electron microscopy, tensile tester and impact tester. The results show that the microstructure of the steel consisted of large amount of acicular ferrite(AF). The AF had substructure of ferrite laths and high dislocation density. The second phase precipitates were mainly in the form of (Nbx, Ti1－x)(Cy,N1-y). After tempering at 650 ℃, the copper which solid solved completely in matrix played a role of solid solution strengthening. The steel had good strength and toughness, and could meet the specific requirement for oil storage tank.