Biodiesel, as a new form of bio-fuel, has developed greatly in recent years. The second generation of bio-energy represented by the lipid from microalgae is one of the long-term strategies to solve energy crisis in the future. However, improving its productivity is still the hotpot in recent years. The aim of this work was to improve the biomass and lipid content of autotrophic microalgae. In this study, we used uniform design to optimize the major culture conditions of autotrophic microalgae in the air-lift bioreactor. The significant regression equations which showed the effects of these conditions on biomass and lipid content of Chlorella C2 were concluded, respectively. According to the significant regression equations, the optimized culture conditions of biomass were: 0.178 g/L the concentration of N5+, 5 L/min air rate, 3% (V/V) CO2 and 6000 lx light intensity. The biomass and productivity attained were 2.11 g/L and 0.352 g/(L·d), 12.2% higher than the highest biomass and productivity obtained [1.88 g/L and 0.313 g/(L·d)] in those experiments. The optimized culture conditions of lipid content were: 0.400 L/min air rate and 1.94% (V/V) CO2. Lipid content attained from the optimized culture condition was 22.4%, 7.7% higher than the highest lipid content (20.7%) obtained in those experiments.