Fixation CO2 with microalgae is a potential promising technique to reduce CO2 emission for its various advantages. In this work, we develop a microalgal fixation CO2 system to capture CO2 from actual flue gas. At first, we evolved a strain Scenedesmus obliquus, named S. obliquus WUST4, with a UV mutagenesis technique, which can endure actual flue gas. The S. obliquus WUST4 can tolerate high concentration CO2, and possesses high CO2 fixation ability. Then, we developed a pilot scale microalgal fixation CO2 system to capture CO2 from actual flue gas with the evolved S. obliquus WUST4. The flue gas was discharged from the combustion chamber in a coke oven. A 100 L air-lift photobioreactor was built in this system. In the pilot scale system, CO2 can be captured from the actual flue gas by the S. obliquus WUST4. The CO2 removal ratio can reach 67% with the optimal operation conditions. This provides an efficient technique for CO2 capture.