Spirulina ( Arthrospira ) has been extensively applied in CO 2 biofixation, wastewater purification, and value-added bioproducts preparation. Light availability plays a pivotal role in Spirulina photoautotrophic cultivation, which is primary determined by characteristics of incident light and distribution of light within photobioreactors (PBRs). To clarify the role of light in Spirulina photoautotrophic cultivation, this review first analyzes the processes of light delivery and conversion in suspended PBRs. Then, effects of key light characteristics, including light intensity, spectrum, and ph...