The utility model provides a double-layer steel chimney, which comprises a plurality of chimney sections, wherein the chimney sections are successively connected; each chimney section comprises an inner wall, an outer wall, a thermal insulating layer and an expander, wherein the outer wall is arranged outside the inner wall; the thermal insulating layer is arranged between the inner wall and the outer wall; the inner walls of two adjacent chimney sections are in mutual lap joint; one end of the expander is fixedly connected with one of the inner walls of two adjacent chimney sections; and the other end of the expander is fixedly connected with the other one inner wall of two adjacent chimney sections. According to the double-layer steel chimney, smoke can be prevented from outwards leaking from the inner wall of the chimney while the next section of inner chimney wall and the previous section of inner chimney wall freely stretch. The double-layer steel chimney has a simple structure and is convenient to manufacture and install.