Light is a key factor for inducing rapidly the astaxanthin biosynthesis. Differed with suspended system, thick algal film in the attached system may cause insufficient illumination for the innermost cells. Thus initial cell amount was set to a high level of 40 g m2 to study the relationships of light intensity with cell growth and astaxanthin accumulation. As the light intensity increased until 120 lmol m2 s1, the astaxanthin content of cells in attached induction increased (Fig 4). And the astaxanthin content reached the maximum under light intensity of 120 lmol m2 s1, and decreased slightly with the increasing light intensity. The biomass productivities were similar under light intensities below 90 lmol m2 s1. In the range of light intensitiesfrom 90 to 160 lmol m2 s1, the biomass increased with light intensity. However, the increase rate of biomass slowed down when the light intensity exceeded 160 lmol m2 s1. These results indicated that the 160 lmol m2 s1 of light density could be considered as the light saturation point (LSP) for this attached induction system in our investigated conditions. This result was different than those in suspended induction that the astaxanthin content was reached the maximum at the light intensity 300 lmol m2 s1 (Li et al., 2010; Liang, 2009). Therefore, the attached induction of H. pluvialis, even at initial cell amount of 40 g m2, can work well under lower light intensity than suspended approach. Furthermore, the attached induction is easy to avoid harmful high light intensity by tilting attached bioreactor toward the light direction, which means more induction bioreactors in the same illumination area can be operated.