Microalgae are widely used in biofuels, medicine, food, and feed industries. However, harvesting microalgal biomass is a major di culty that hinders their industrial application. In this study, three occulants (ferric sulfate, sodium hydroxide, and chitosan) were used to harvest the marine microalga Chlorella vulgaris, and oc characteristics including occulation e ciency, concentration factor, and ocs morphology were studied. The results showed that the tested occulants can e ciently harvest C. vulgaris. The occulation e ciencies of ferric sulfate (0.9 g/L), sodium hydroxide (0.6 g/L), and chitosan (30 mg/L) were 93.4% ± 0.8%, 96.5% ± 0.6%, and 98.8% ± 1.3% within 70, 100, and 12 min, respectively. The total carbohydrates, proteins, and lipids contents in C. vulgaris were not in uenced by the test occulants after harvesting. When compared with fresh f/2 medium, the recycled medium could also e ciently support C. vulgaris growth. Among the three occulants tested, chitosan was ideal owing to its high e ciency, low dosage requirement, short harvesting time, and reutilization of culture medium.