Abstract: As an important raw material for the extraction of natural astaxanthin, Haematococcus pluvialis is usually harvested by natural sedimentation or centrifugation. However, these harvesting methods either take a long time or consume a lot of energy. This study proposed an efficient method for the harvesting H. pluvialis using pH-induced induced dissolved air flotation (DAF). Harvesting efficiency and solid content, as well as their kinetic curves, were adopted to investigate the influence of pH on the pH-induced DAF harvesting. In addition, the harvesting performances of pH-induced DAF was compared with those of pH-induced sedimentation, chemical coagulant (aluminum sulfate)- and biological coagulant (chitosan)-induced DAF, based on the efficiency and residual metal contents in the harvested biomass. Whether pH treatment affects the astaxanthin content in the harvested biomass was also evaluated, comparing with the content in centrifugation harvested biomass. The results showed that auto-flocculation occurred when the pH of the media was decreased or increased, facilitating the flotation harvesting and sedimentation harvesting of H. pluvialis. pH-induced DAF obtained higher harvesting efficiency and required less separation time, comparing with pH-induced sedimentation. When pH was adjusted to less than 3 or greater than 11.5, the harvesting efficiency of 95% was achieved in 2min using pH-induced DAF, while that took 30min for pH-induced sedimentation to achieve 80%—90% harvesting efficiency. When the initial concentration was 3.2 g/L, the solid content of biomass harvested by pH-induced DAF can reach 17%, realizing 53 times concentration, which was much higher than those harvested by pH-induced sedimentation. Most importantly, pH-induced DAF performed as well as aluminum sulfate and chitosan coagulants induced DAF, while avoiding the impurity of biomass caused by chemical such as Al³⁺. The astaxanthin contents in H. pluvialis biomass harvested by pH-induced DAF were not affected by the pH treatment. Therefore, harvesting H. pluvialis by pH-induced DAF proved to be a rapid, efficient and environmental sustainable technique, which shed a light on the process development of mass production of H. pluvialis biomass.