Oleaginous microalgae can produce biodiesel by solar energy, transforming the inorganic carbon into organic carbon. However, the reduction of the energy consumption in the process of oleaginous microalgae cultivation is the bottleneck to achieve large-scale production of biodiesel. By the optimization of the Chlorella sp. cultivation in an airlift photobioreactor, as well as the energy calculation and comparison of different culture conditions, the work proposed that, the adoption of optical fibers as the internal illumination source and a proper flow rate (0.6 L／min) in the cultivation of Chlorella sp. in the airlift photobioreactor could enhance the energy efficiency and obtain the maximal productivity per energy consumption 4.40 g／(W·d), 8-25 folds of those with the external illumination conditions.