Steel-frame stair structure and its construction method

A steel frame stair structure is provided to elevate the structural strength of the whole staircase and simplify the working process by installing the pre-assembled steel frame stair frame and then constructing the concrete structure such as vertical walls and slabs. A steel frame stair structure is composed of plural steel frame columns(11) vertically mounted; plural embedded angles horizontally connected between the steel frame stairs; steel frame stairs(15) connected to the embedded angles in zigzag; and mutually assembled first and second steel frame stair frames(10,20). The second steel frame stair frame is assembled at the upper side of the first steel frame stair frame. The embedded angles of the first and second steel frame stair frames are mutually combined through a male-female method at the upper side of the first steel frame stair frame to assemble the second steel frame stair frame.