Due to the complication of the smoke duct welding of the No.1 unit in China Power Investment Corporation, Sichuan Fuxi Power Plant, the CO2 shielded arc welding technology is used. This paper introduce the feature and measurement of CO2 shielded arc welding technology. The techno-economic analysis is conducted comparing with traditional hand welding technology. The results show that CO2 shielded arc welding technology improves welding quality, and saves costs.