To meet the demand for scenery-matching stack system, we have developed semi-monocoque structure, It has been applied at Misumi Power Station of The Chugoku Electric Power Co., Inc., which is under construction. This stack system consists of an inner shell, the smoke outlet, and an outer sell to support it. The outer sell is of semi-monocoque structure consisting of thin steel panels, columns and ring members, that has helped decrease in steel weight. We have also adopted a vibration prevention structure consisting of springs and dampers located between the outer shell and the smoke outlet for decreasing resonant vibration by wind and seismic response. We have used the large block construction method, dividing the outer shell into approximately 40 ton panel blocks, and construction them by a large-sized tower crane at the site.