Abstract: A steel post is composed of an outer tube, an inner tube, two retaining members, a position confining member, a fastening member, and an elastic element. The inner tube is received in the outer tube such that the inner tube can be extracted and retracted, and that the extrated inner tube is located by the clamping mechanism of the retaining members. The displacement of the retaining members is confined by the position confining member. The fastening member serves to fasten and unfasten the retaining members so as to enable the extracted inner tube to be retracted. The elastic element enables the retaining members to remain disengaged with the inner tube.