The multiscale strategies were systematically designed and operated for efficient capture and the bioconversion of CO<sub>2</sub> using microalgal biomass under photoautotrophic condition. In microscale strategy, the relationship between phototaxis and photosynthesis was revealed using microfluidic device. In bench scale strategy, an autotrophic astaxanthin production was improved by highly photosensitive mutant and Habber-Weiss Reaction (Superoxide-Driven Fenton Reaction) under high temperatures in Haematococcus cells. In pilot scale strategy, a closed-photobioreactor with a vertical bubble column type easy to scale-up and efficient for capture of CO<sub>2</sub> was developed. In our work, particularly, an industrial flue gas and sunlight were used for an economical microalgal culture system. The microscale approach fit for strain improvement insures the simple strategy for isolation of highly efficient strains in photosynthesis. The benchscale approach is suitable for process development and will be useful for application to pilot scale. These two approaches will synergically improve the pilotscale approach which is crucial for commercialization of the autotrophic microalgal system.