The invention relates to a method for culturing microalgae by utilizing flue gas of a coal fired power plant, comprising the following steps of: firstly, introducing flue gas to a CO removing tower, and leading the trace amount of CO and NO to generate CO2 and N2 under the catalysis of active semicoke; leading the flue gas from the CO removing tower to enter a desulfurizing tower again, oxidizingSO2 in the flue gas into SO3 under the catalysis action of active semicoke by utilizing O2 contained in the flue gas, and absorbing the SO3 on a catalyst; leading the flue gas to enter a denitrifyingtower after passing through the desulfurizing tower, oxidizing the NO in the flue gas into NO2 under the catalysis of active semicoke by utilizing the O2 contained in the flue gas, and absorbing the NO2 on the catalyst; and introducing the purified flue gas to a microalgae culturing device, fixing the CO2 in the flue gas by oily microalgae and then passing through a flue gas-flue gas heat exchanger, and finally, exhausting the residual flue gas through a chimney. In the method, the flue gas of a thermal power plant is taken as one of raw materials for microalgae culture, high-quality oily microalgae is obtained as oil-producing materials, not only the environment is governed, but also fuel is produced, therefore, the method has very important social, economic and environmental benefits.